In modern-day Tokyo, father Yuichi spends his time by his comatose son's side after an incident where
someone pushed the boy off a roof. Yuichi's father the Elder comes to visit as well, but
he's harsh instead of supportive as wonders where he was when his son needed him. Sometime later,
Yuichi retrieves his gun, deciding it's time to get revenge. Meanwhile a very unlucky American
mercenary walks the city streets while talking on the phone to his handler Maria, who gives
him the codename "Ladybug" as a pun for his bad luck. The mission is simple: he must board the
bullet train and steal a mysterious briefcase that has a sticker on the handle. This assignment was
supposed to go to another mercenary called Carver, but he couldn't make it because he was sick. Once
he reaches the station, Ladybug accidentally bumps against Yuichi, which causes him to drop
his locker key and ticket without noticing. Fortunately, Ladybug knows how to pick locks
and manages to open the locker anyway, earning him access to the sleeping powder he had requested but
refusing to take the gun. Ladybug has to convince the conductor to let him in with just the receipt,
but Yuichi boards with no issues and follows the instructions on a note sent to him by the person
that tried to kill his son. However who he finds on the seat is a young, adorable girl, and Yuichi
thinks he did something wrong until the girl tases him. This is Prince, a young woman that uses the
innocent girl act to commit crimes. Following Maria's instructions through an earpiece, Ladybug
finds the briefcase in the luggage rack at the end of the carriage, not knowing it belongs to a
pair of assassin brothers codenamed Tangerine and Lemon, who are aboard as well. The sticker on the
briefcase comes from Lemon, who is obsessed with Thomas the Tank Engine metaphors and even carries
a sheet of Thomas stickers with him. The siblings aren't here only to protect the briefcase though,
they've also kidnapped the Son of White Death, the most dangerous mafia boss. He hired the brothers
to keep his son out of trouble and take him back to his father together with the briefcase full
of the ransom money some enemies of White Death owed him. Tangerine gets regular calls from their
handler to check everything is fine, but when Lemon double-checks the rack, he discovers the
briefcase is gone. Lemon isn't worrying because he thinks delivering the Son alive is the most
important part of the mission, so Tangerine has to tell him the whole story of White Death to
make him understand. The Japanese underworld used to be ruled by a man named Minegishi;
who was known for his brutality but also for his loyalty. One day, a former member of the
Russian mafia joined Minegishi's clan and worked his way up the ranks until he became an advisor.
The other advisors didn't trust him and tried to warn Minegishi, but he didn't listen and such a
decision became his downfall. The Russian man, who became known as the White Death,
made his own gang and killed Minegishi and all his men in one single night. Now he's known as a
soulless psychotic killer in charge of the largest criminal organization on the planet, although he
hasn't left his compound since his wife died in a car accident. This is the reason why he hired the
brothers instead of coming for his son himself, he wanted the pros that worked on the infamous
Bolivia job. They need to recover the briefcase immediately, yet when they go back to the Son
to explain the change of plans, the siblings find out things have gotten way worse: the Son is dead,
and whatever killed him left him bleeding from his eyes. Back to Yuichi, he finally wakes up
and discovers Prince has rigged his gun. She also has a henchman in the hospital, so if Yuichi kills
her, his son dies as well. Prince knows Yuichi works for the White Death and he delivered a
briefcase two days ago to one of White Death's associates; that's when she saw her opportunity:
if she followed the briefcase, she could find the White Death. The reason why Yuichi is here is that
Prince wants him to kill White Death for her. Meanwhile Ladybug has fled to another carriage
and is getting ready to get off the train at the next station, but he finds the door blocked by
the Wolf, a mercenary who worked for a dangerous Mexican gang. Weeks ago on the day of his wedding,
he accidentally spilled his glass of wine, and this delay in drinking saved his life: his wife
and all the guests died of whatever poisoned their drinks, left with their eyes bleeding.
Wolf was told that the person responsible for those deaths is on the train and has come to get
his revenge. A fierce fight starts between both mercenaries that takes them to the train's bar,
where Wolf manages to stab Ladybug only for his phone to take the hit. After exchanging a few
more hits, Wolf throws his knife at Ladybug, but since he uses the briefcase as a shield,
the knife bounces and stabs Wolf instead. The train is about to approach another stop, so the
brothers clean up the Son and cover his face with some funny glasses before getting ready to get
the briefcase back. Lemon guards a door to check every passenger getting off, and Ladybug sees him
when he's about to leave, remembering Lemon as the man that tried to kill him during a mission
a few years ago. Since he can't use this exit, Ladybug runs through the other carriages and bumps
against the train's mascot, who tries to take the briefcase from him. After punching its adorable
face, Ladybug runs to the next exit, but it's too late: the doors are closed and the train takes off
again. Then, Ladybug returns to the bar, hides the briefcase, and takes Wolf's phone to call Maria,
who confirms the story: the objective of the wedding assassination had been to get Wolf's boss,
and everyone else fell too just for being associated with him. Ladybug had infiltrated
that wedding too as a waiter and had been the one that accidentally made Wolf spill his glass,
but he hadn't been the one behind the deaths. While trying to think of what to do next, Ladybug
notices Tangerine looking for the briefcase and decides to hide in the luggage rack. Tangerine
sees him anyway, but luckily, he doesn't recognize him from that old mission and keeps on walking.
Next, Tangerine bumps into Prince and Yuichi, and when he asks if they've seen the briefcase, Prince
tells him Ladybug's description, since she saw him run by earlier. In the meantime, Lemon returns to
his seat while receiving a text from his brother with the description just in time for Ladybug to
sit across from him. Ladybug doesn't want to mess with dangerous people and offers a deal: he'll
give them the briefcase back if they don't kill him. Lemon would love to accept but he doesn't
want to play nice after Ladybug already killed someone - he's referring to the Son, but Ladybug
thinks he's talking about Wolf. Still stuck on the train metaphors, Lemon calls Ladybug "his Diesel"
and begins fighting him, but Ladybug manages to knock Lemon out before he can use his gun. Then,
he fills Lemon's water bottle with sleeping powder, hides the gun in the luggage rack, and
discovers Son's body, which has the same bleeding eyes as the people in Wolf's wedding. Meanwhile,
Tangerine also makes his way back to the carriage, Ladybug steals Lemon's phone and gets out of there
as he calls Maria to inform her someone else on the train besides he and the siblings are
doing a job since it can't be a coincidence that Wolf's family and the Son were killed
in the same way. While talking, Ladybug tries to block the door between carries with luggage,
which causes him to accidentally open a cage with a snake that was stolen from the zoo a few days
ago. The poison of this snake is what causes the bleeding effects shown by the Son. After finding
Lemon unconscious on his seat, Tangerine continues his search for Ladybug, who is now trying to hide
from the conductor because he should've already gotten off. Knowing Tangerine is after him,
Ladybug approaches the Passenger and pays him some money to exchange clothes. By the time
Tangerine gets there, he approaches the Passenger by mistake, giving Ladybug the chance to escape.
Meanwhile, Prince and Yuichi go to the bar to find the briefcase. Then, they hide in the bathroom,
where Yuichi gets a call from the Elder that Prince makes him put on speaker. The Elder wants
to know why Yuichi left the hospital, and Prince orders him to be honest, so Yuichi explains he's
here to get revenge. This is disappointing for the Elder to hear, but before Yuichi can reply,
Prince makes him hang up. Now Yuichi will stay in the bathroom trying out all possible combinations
until he opens the briefcase while Prince stays outside keeping up the innocent girl act. She
also throws Yuichi's phone away to avoid any more distractions. Back to Tangerine, he returns to his
brother's side and wakes Lemon up, who is starting to think Ladybug didn't kill the Son. Their chat
is interrupted by a call informing them that instead of going to Kyoto, the brothers must
get off with the son and the briefcase at the next stop. There's a group of yakuza gangsters waiting
for them, but the siblings already suspect it's a trap and think of a plan. Tangerine gets off alone
and tells the henchmen that he's a professional that doesn't fall for cheap tricks, therefore
Lemon is still inside guarding the briefcase and the Son, who is now waving through the window
as Lemon guides his movements like a puppet. Thankfully they buy it and Tangerine gets to go
back in one piece, so now the brothers must split and search both ends of the train for Ladybug.
Before leaving, Tangerine gives Lemon his gun for extra protection. After they're gone, Prince comes
to check on the Son, spitting on his face when she notices he's dead. Then she goes back to the
bathroom, where Yuichi has finally managed to open the briefcase. However Prince isn't interested in
the money, she just wants to plant a bomb inside so it can kill White Death when he opens it. It's
the same mechanism she's rigged Yuichi's gun with, inspired by the fact every time someone
tried to kill White Death, he killed them in return with their own weapons. In the meantime,
Ladybug's hiding in a different bathroom while Maria explains a famous surgeon that operated on
gangsters was killed in the middle of a procedure by the same eye-bleeding poison. The assassin's
name is Hornet and Ladybug needs to find them to hand them to the siblings to secure his own life.
Using Lemon's phone proves to be a bad idea when Tangerine manages to find Ladybug in the
bathroom thanks to the tracking app. Another fight starts and both assassins exchange plenty of hits,
only stopping when Tangerine needs to pick up a call from White Death's henchman. This time, he's
told to get off with the briefcase at the next station or everyone on the train dies. Tangerine
doesn't know what to do, but Ladybug comes up with a plan: since the gangsters don't know what Lemon
looks like, Ladybug will pretend to be him. The guys get off at the next station with a random
briefcase they stole, but their plan goes sour when the briefcase accidentally opens and reveals
it's not the one with the money. Fortunately, before White Death's henchmen can catch them,
Ladybug and Tangerine run back inside right before the train takes off again. Speaking of Lemon,
he's still looking for Ladybug while drinking his water, and he comes across Yuichi and Prince,
who plays the innocent girl card again when asked about a suspicious man with a case.
However Lemon doesn't believe her because she specifically mentions not seeing a briefcase, and
he never used that word, which means she is his diesel. To make them talk, Lemon shoots Yuichi,
then he and Prince hide the body in the bathroom. Lemon turns onto Prince next, but at that moment,
the sleeping powder kicks in and he passes out, so Prince steals his gun and shoots him before hiding
him in the bathroom too. Before leaving, she ties the doorknob up to prevent anyone from escaping.
At the next stop, Ladybug tells Tangerine where he hid the briefcase and tries to get off,
but Tangerine doesn't let him because he still needs a fall guy. Seeing he has no other choice,
Ladybug kicks Tangerine off the train right before it takes off again, but this isn't enough:
Tangerine runs after the train and jumps on its tail to then get back inside by breaking a window.
Meanwhile, Ladybug is changing carriages and finds Yuichi's phone when it rings. The Elder is trying
to check on his son, but Ladybug hangs up on him after telling him to use the tracking app. Then,
he makes it back to the bar, and after finding the rigged briefcase right where he left it, he checks
Wolf's body again to look for clues. It turns out he's come to kill the Hornet, who has been hiding
inside the mascot costume all this time and she was the one to kill the Son; she also sneaked
into the wedding by pretending to be the chef. Hornet finds Ladybug first though, approaching
him after stealing the uniform from a trolley employee. A new fight begins as Horney explains
she was promised the money from the briefcase before stabbing Ladybug with a needle full of
poison. Thinking quickly, Ladybug grabs the needle and stabs her in return, prompting Hornet to take
out the antidote with the intention of curing herself. However Ladybug steals it for himself and
leaves her to die. Back to Tangerine, he finds the bathroom with the tied doorknob and opens it to
find the body of his brother. Grieving, he takes off his necklace and puts it around Lemon's neck
before taking the gun from Yuichi's hand, ready to get revenge. Next, he calls White Death to tell
him to meet him at the end of the line of Kyoto because he should stop being a coward. He isn't
afraid of the train blowing up because he can't kill all the passengers, but White Death reveals
he knows only the mercenaries are left inside and all the civilians have already gotten off because
he bought all the tickets himself. After White Death hangs up, Tangerine comes across Prince,
who pretends to be an innocent girl again and cries as she makes up some story up. At first,
Tangerine believes her, but when Prince turns around, Tangerine notices a sticker of the
character Diesel that was put on her back by Lemon before he was shot. Tangerine realizes Prince has
been the bad guy all along and tries to shoot her, but Ladybug shows up then and believes Prince's
crocodile tears, so he jumps on Tangerine to stop him. In the struggle, the gun is accidentally
fired and kills Tangerine. The train is about to stop at the next station, and Ladybug promises to
protect the girl. Since Prince needs to reach the end of the line, she pretends her bag is stuck and
begs Ladybug not to leave her alone because she's scared, thus once again Ladybug misses his chance
to escape. Ladybug may've left but someone did get in: the Elder, who followed the advice of the
tracker app. As soon as he walks by, he recognizes Prince's voice from when she interrupted his call
with Yuichi and sits across them. Ladybug tries to grab the gun that Prince claimed she found
laying around only to end up bitten by the snake. Panicking, he runs to the bathroom to throw the
snake in the toilet, and thankfully he doesn't die because the antidote is still working. Meanwhile,
the Elder grabs Prince's bag and realizes she's the one that pushed his grandson off the roof,
so Prince explains she needed Yuichi to help her kill the White Death and that had been the
only way to get him on the train. She tries to imply both Yuichi and his son are dead,
but the Elder isn't scared of her tricks: he left a bodyguard at the hospital, and she's already
killed Prince's henchman. Finding herself without the upper hand, Prince runs to another carriage
while Ladybug comes back to sit with the Elder, who decides to share his story. When he was a
young man, the Elder made a promise to provide for his family no matter the cost, that was why
he became an important member of Minegishi's crime family. He had been one of the advisors
that warned Minegishi about the White Death and got ignored, and he survived only because fate
wanted him to. When he returned home, the Elder found his wife dead and the house destroyed,
the only survivor being Yuichi. Afterward, he went into hiding and concentrated on finding a way to
get revenge without putting his son in danger, but White Death always stayed out of reach. Now
though, the Elder thinks fate has put White Death in his path by guiding him to the train. The men
agree to work together and go to the bathroom, where they find out Yuichi is alright because the
bullet didn't hit any organs, and Lemon is also fine because his bulletproof vest caught Prince's
shots. However his mood tanks when he finds the necklace around his neck. After saying goodbye
to Tangerine's body, Lemon comes after Ladybug and Yuichi, hungry for revenge. The Elder stops him,
reminding him they must work together if they want to survive the White Death. Moments later
the train makes it to Kyoto, where the White Death is waiting for them with his army of assassins.
Ladybug comes out with the briefcase, intending to buy the team some time, and the henchmen capture
him before they begin arguing over who gets to open the briefcase to check its contents. In the
meantime, the White Death gets on the train and comes across Prince, who is revealed to be the
White Death's daughter. He always wanted a boy and that's why she got that nickname, which she
resented. She also hated her younger brother for getting all their father's attention for being the
heir even when he was a good-for-nothing loser. Prince has built her career as a mercenary based
on nothing and now she's here to make her father see her for whom she really is. As she expected,
White Death takes the rigged gun from her, yet he doesn't kill her, claiming he's always seen
her but she's never been part of his plan. While Lemon goes to the control room and tries to figure
out how it works, White Death goes to check on the state of the briefcase and confirms Ladybug's
theory: all the assassins that were on the train had been hired by him, expecting them to kill each
other. It was all part of White Death's plan to take revenge for what happened to his wife:
the siblings' Bolivia mission had consisted of killing a huge group of White Death's crew,
so he had to travel there to take care of it and left his wife alone. It should've been him in the
car that night, since it hadn't been an accident, it had been an assassination attempt against him.
She could've survived if the gang's surgeon had been available, but Hornet had already killed him.
The Son went down because he had gotten in trouble again and his wife had gotten in the car to help
him, and Ladybug was brought here by mistake: White Death had wanted Carver because he had been
the mercenary that killed his wife. Before Ladybug can explain the confusion, the henchmen finally
open the briefcase and the bomb goes off. Yuichi and the Elder begin fighting the gangsters that
were looking for the bodies, and Lemon finally manages to start the train again. The explosion
knocks Ladybug, White Death, and more of his crew into the train before it takes off, and now they
join the fight as well. The Elder goes hand to hand with the White Death and almost loses,
but Yuichi comes to his rescue and knocks White Death back by tossing a water bottle at his face.
This gives the Elder the chance to finish him with his sword. Meanwhile Ladybug reaches the control
room and tries to help Lemon find the brakes while fighting the henchmen coming after them,
but Lemon sacrifices himself to push the last gangster off the train, falling to the water
with him. Ladybug tries to force the brakes by cutting some wires, causing the train to get off
rails and crash into downtown Kyoto. The Elder and Yuichi save themselves by holding onto a seat, and
Ladybug survives thanks to his landing against the soft mascot costume. Once they get off the train,
they discover White Death is still alive, but he falls for the Prince's rigged gun and ends
up dying anyway. The trio thinks they're safe to leave now, but Prince shows up next ready to
claim the name of White Death, only to suddenly be run over by a truck filled with tangerines.
It turns out that moments ago, Lemon safely swam out of the river and, while running down the road,
he saw the tangerine truck and considered a signal. After stealing the truck, he used it
to kill Prince as revenge. After Yuichi and the Elder leave, Ladybug sees a fancy car
arrive and is shocked to discover Maria has come to pick him up. Unfortunately, she immediately
falls victim to Ladybug's bad luck, and her car ends up destroyed by a falling light post.