Before I answer your question, this is a comment that I copied from someone in chapter 4 comment section, you go thank him later.
Oh, and before I go into this, a HUGE warning to anyone reading this. This has some nasty shit that might make you feel disgusted.
So yeah both the yankee and the teacher are the same person. No split personalities or something like that. The teacher is an ojou-sama (rich lady) who becomes a biker yankee during high school as an outlet for her stress/pressure from her father and smth else which we'll cover soon. She comes to very like this lifestyle. She has a couple of other yankee friends who are also rich ladies, and the lady she stays with while in yankee mode is her mother or the new wife of his father? (Surprise reveal at the end). The father and brother? don't seem to be that bad (good at heart probably), it's probably a miscommunication or something.
As for how to story progresses, the first couple volumes (I assume) focus on the developing relationship between the yankee/teacher and the student. I really don't know why fmc fell for mc, probably because he has a pure heart or kindness (this may seem like bs but is relevant to why she fell for him) This is the 4 English chapters and 5-10 or 12 of the Indonesian chapters.
The last couple volumes (spanish chapters) is where the story feels really disgusting to read (feels like an ntr story and vibes).
So in the past, yankee had a douchey older tutor (college aged I think), to prepare her for the high school entrance exams. Feeling isolated from her family, douche takes advantage and starts a secret intimate relationship with yankee. And yes, they go all the way. That's why when she took mc virginity, she said it was her second virginity, ie second man to have sex with her.
And by God, he films a sex video of her. He wears an animal mask to hide his face and yankee starts to masturbate in front of the camera, doing what 'sensei' tells her to, because 'sensei' knows what's best for her. The manga doesn't show them have sex, but that much is implied in the video. MC, in finding the video, goes full kazuya/rental girlfriend and jacks off to it. Pathetic. Tutor is probably why the yankee became so horny and erotic.
Anyway, the family finds out their relationship and kick out the tutor. I think they knew about the relationship but not that they were intimate. Douche keeps the video and threatens yankee to keep their intimate relationship a secret, or he'll release the video and ruin the reputation of her and her family, which is the last thing she wants, especially due to the strict relationship with her father. Yankee enters high school and makes friends, and together they confront douche to get rid of the video, but it fails (idk why). Of course, by the end of all this, fmc regrets this relationship and doesn't get with anybody until she meets with mc. As for why she initiates a sexual relationship with mc under the yankee side, I don't really know. Maybe it's something like showing the true side of her to mc, but idk I'm just spit balling here.
So with that over with, douche reappears and meets mc and fmc and does the classic douche thing of 'you don't know the true side of her' and the 'I know her secrets that she never tells anyone' and one more 'you don't know how she really is'. And then sends the video to the mc, hoping to alienate him from fmc. MC jacks off, and then seeks advice from yankee mother?, and then does the thing every ntr protagonist couldn't do: report the video to the police since douche is in possession of cp. Though before reporting the video, fmc teacher mode finds out mc saw the video, runs away, mc finds her, he tells her he loves her, they make up, have sex (first time in teacher mode), he realizes yankee and teacher are the same person, and both decide on a plan to take down douche without him spreading the video anonymously in the internet, before reporting him to the police. Cause once something is up on the Internet, it never comes down. I think they do this cause douche knows that if he goes down, he's taking everyone with him.
So last couple chapters they confront douche, yankee brings her friends and other biker friends, douche is cornered but threatens to release the video, fmc said fuck it and release the video, she don't care about anymore, and then douche proceeds to upload the video, though not before yankee's father pulls up and whips out his fucking hunting rifle and shoots the living fuck out of his phone hahahaha. Of course, with the phone gone, douche is taken down and all is well. Father reveals he also had a yankee past, accepts his daughter and admits his mistakes. MC then asks out the fmc, she accepts, and they get married at the end.
Man, what a story. I heard this artist made doujins, right? Cause this story does feel like it comes straight out of a doujin.
