She seems to have taken the phrase "go fuck yourself" far too literally. And somehow ended up with Operation Mindbreak your Teacher Inside Your Own Body.

Base +10, IvanisBest +7, Eclipse131 +6, Mocka +20, Kraftz +6, Mirarin +7, silv1 +6, Soldier A +6, James2841 +6, BonoBono08 +6, Ildzmer +7, IncognitoMaud +6, SuspiciousElephant +4, and 1 more...

RAW: https://e-hentai.org/g/1421251/17ea9f7b7a/

CHN: https://e-hentai.org/g/1572015/21354acf5a/
KOR: https://e-hentai.org/g/1424476/2fc3b6e854/

Base +19

got a little blurry there because they swapped bodies but had the bodies memories, did they switch back at some point?

Base +7, Serena Lea +7, Ildzmer +7

Mai's ego stays intact in sensei's body, sensei's ego is assimilated over time into Mai's body, essentially becoming Mai completely. Kind of defeats the purpose of making sensei her lover if he becomes her leaving nothing of him behind. If she wanted to win him over, she'd have switched back.

Base +6, Kraftz +6, yaque +6, Quasi-Evil_Overlord +6, Mirarin +7, Ouroboros186 +6, Paulie22 +6, xaelath +6, Serena Lea +7, Divine God of Lust +6, Soldier A +6, RighteousSwordhand +6, BonoBono08 +6, and 12 more...

I don't think he really becomes her. His personality never quite matches what hers was at the beginning. It's more like his sense of self is trying to reconcile itself with her memories in lieu of his own. So he still thinks of himself as an adult, but the reasoning behind it shifts to match his new memories until it's more like a kid's "I'm a grown-up, so treat me like one." Basically, he's working out what he would be like as a little girl (who is extremely horny for Sensei). Presumably the same thing happened to her, just to a lesser degree.

Though I agree that this sort of story doesn't really make sense unless the initiator is either a possessive yandere or has a reason to want out of their body/into someone else's. Especially when she's giving up a decade or two of her life to do it.

Base +7, James2841 +6, Paulie22 -6, Ildzmer +7, Kraftz +6, falafelswoop +6, Kotovsky +6, Saa-Chikou +10, Psychotic Pastry +6, blackpillow +8, jsnormandy +9, Kurogal +18

When your particular fetish is the Ship of Theseus.

Base +6, Echoleon +6, xjaja0 +7, Ampff +6, DatAtlas +6, taroham +5, Kotovsky +6, reckless1000 +5, Psychotic Pastry +6, blackpillow +8, TheShortKeys +6, Seaguller +6, Azuelle +5, and 5 more...