One day, Kiku finds a handsome naked man named Heracles wandering the streets and ends up taking him in. He learns that Heracles is actually a sexbot programmed to become a completely obedient sex slave to the first person he has penetrative sex with (whether topping or bottoming).

The catch is that Heracles has developed a personality of his own and has decided that he doesn't want to become a mindless sex slave and wants to develop his identity and knowledge of the world more. Unfortunately, it's difficult to overcome his basic programming of having sex with the nearest person at any opportunity and he winds up trying to seduce Kiku repeatedly even though he's painfully aware that he'll lose any sense of identity he has if he goes all the way with Kiku and isn't even sure if his growing feelings for Kiku are that of genuine love or just programmed desire.

1st bonus: As part of his programming, Heracles proposes sex as a solution to any problem. Can't sleep? Sex will tire you out and help you fall asleep more quickly! Feeling sick? Sex will make you sweat more and help bring that fever down! (this one was actually proposed in a Giripan doujin).
2nd bonus: The two do eventually have hot sex; there are many forms of non-penetrative sex, after all...