Girls on the Brain! X4000, 1

When you wake up after hitting your head, your sex drive will be multiplied by 4000?! The battle between Seigo and his sexual desire begins now. On one side is Seigo Hasegawa, a man who has suddenly acquired a cheat sex drive, and on the other is his friend An Yagami, who feels responsible for Seigo's new problem and tries to help him.