It kinda feels sad because shy uke doesn't even remember what happened afterwards and he is not in control of his body when seme do it with slutty uke so he's not even aware that he's doing it with seme
So it's not like they are the same person, it's like two different people living inside the same body and it's even more sad because shy uke has unrequited love towards seme but the one who did it with seme, kissed him and seduced him first was the slutty uke
Another thing it's that seme didn't even fuck the shy uke in the threesome scene (when the scientist separated the slutty uke from shy uke body for a day). He only "fucked" the shy uke (more like forced himself) when he thought he was the slutty one
In the final chapter the slutty uke was still taking control of shy uke's body to do with seme
The original version (shy uke) is being cucked by his own slutty version
I mean.. maybe I'm thinking too much into this but this was unsatisfying to read lol
I think everyone is thinking to deep about the split personality stuff. The “slutty” uke is technically still the same uke, if anything it’s his true self when he’s not suppressing his emotions so it only makes sense that that’s the version we will see during sex when he’s letting his true emotions out