Depending on the erotic manga by Kaizuka.
An alien crashes into Amano Inori although fixing her body, makes her smarter, more athletic, prettier, and increases her bust size about five cups accidentally.
The alien then requests to watch her, since he stumbled on Earth to observe humans anyway, and really do everything to her until she sees Sugiuchi and Amano Inori get horny.
The alien then manipulates Amano Inori's body and makes her start having sex with Sugiuchi.
