Tarantino makes bits of his movies look like bits in other peoples movies. He is not a plagiarist -- far from it. He wants to remind you of other movies because he is conversation with other filmmakers, often figuring how to trump them, even his buddies.
Special warning on this post: Ichi the Killer is famously one of the most violent movies ever made. The clips below reflect some of that.
FROM ICHI THE KILLER
a guy turns around and smokes a cigarette. he has big slits in his cheeks and the corners of his mouth are held together with piercing. When he blows the smoke out it comes out of the slits not his mouth.
FROM ICHI THE KILLER
A guy has a heel with a short blade in it. He does this fast move at this dude. The dude is shocked and says something brief. Then he unrealistically splits in two from head to crotch. You can see some of this here but be warned it is extremely violent:
FROM KILL BILL
In her fight in the House of the Blue Leaves with the Crazy 88s Thurman slices through a guys cheeks then immediately cuts a guy down the middle from head to crotch splitting him into two halves.
Ichi the Killer, directed by Takashi Miike, is a story of gang warfare. Ichi is a "murder savant" as my friend Tim puts it. He has a handler, who has him sort of brainwashed, and who sends him at targets, members of his old gang. Ichi can only get sexual satisfaction from sadism -- in one of the most crazy scenes the opening title rises from a pool of his ejaculate after he watches a woman get beaten and raped. Ichi kills a boss but it is cleaned up so it appears the boss disappears. The boss's right hand man Kakihara goes looking for him, by torturing lots of people, including people in his own gang. Kakihara is a very brutal sadist and a masochist who longs to be tortured as he tortures others. When he catches wind of Ichi he becomes very excited that this super killer could finally bring him the pain he wants. But their meeting is a total anti-climax as Ichi breaks down crying and Kakihara does not get the duel he wants. What happens after that does not make much sense (Kakihara hallucinates Ichi attacking him and kills himself, but then is alive later unhurt and someone hung the handler?). You watch it for the crazy killings.
The scenes above feature the first time we see Kakihara, as well as Ichi killing the guy who was beating and raping a woman. How he was able to inflict that wound with a blade in his heel that looks to be an inch long I really don't know, and it is part of what makes the scene funny. One of the things I don't like about Ichi is how it combines realistic violence such as women being beaten and raped, and this kind of wacky crazy violence. I want just wacky crazy violence thank you.
Tarantino really enjoys the films of Takashi Miike. I had not expected much of a connection to Kill Bill really -- Ichi is a violent film, Kill Bill is a violent film, and naturally there was going to be some coincidental overlap, as we have seen in past movies involving arm severing (Tenebre) and eyes bleeding (City of the Living Dead), both kinds of violence that show up in Kill Bill. But the Ichi connection turned out to be a real one, one that seems to me to be deliberate. The two most memorable things about Ichi the Killer are Kakihara's mouth slits and the dude that gets sliced in half top to bottom. So I don't think it is a coincidence that in the melee at the House of the Blue Leaves Thurman cuts a guy's cheeks open leaving him with slits in both (a very unusual and unexpected wound you would not expect in the scene), and then immediately and impossibly cuts a dude in half top to bottom. In a battle where she kills like 60 guys two examples of Ichi-trademark violence are right next to each other.
This re-incorporation of two images from Ichi takes a problem in Ichi and addresses it. Ichi is known almost exclusively for its violence. Tarantino takes what works in Ichi and gives it a context that works better than the non-voilent parts of Ichi. He gives it a story that makes more sense, with more human and believable characters. He takes what works in Ichi and leaves what does not work behind. He says "hey, I love me some splatter but wouldn't it be better if that splatter was a part of a movie that had more sympathetic characters, so you did not spend the non violent parts of the movie waiting to get back to the violence?" I think it is actually a very powerful revision, one that both celebrates Ichi and also demolishes it, which is kind of what I expect allusion to do when used properly.
There is to my eye another bit lifted from Ichi for the same reason:
FROM ICHI THE KILLER
A man in tortured -- his cheeks are pulled very hard away from his body by two people. The flesh is unrealistically stretched.
FROM KILL BILL
Thurman bites the lip of her rapist and the flesh is unrealistically stretched.
In the Ichi clip Kakihara continues to investigate what happened to his boss through torture. Tarantino takes and uses the stretchy-flesh violence in Kill Bill for a rape scene, which something Ichi returns to again and again. I feel like you don't see stretchy-flesh violence that often. Except Tarantino's revision of Ichi is that the woman is able to save herself, something that does not happen in Ichi, where the woman who is saved by Ichi is immediately and non-sensically killed by Ichi. Tarantino is all about having his women be in the same position as other film characters but giving them lots of agency and control and general kick-assery.
In Kill Bill Tarantino gives Thurman access to the kind of extreme violence Kakihara and Ichi inflict, as well as the violence that was inflicted on Kakihara. She is the inheritor and controller of a great tradition of extreme violence as Tarantino is.