Denma Onna to Seikan Otoko

The protagonist, Suga Kanichi, appears to be a normal guy, but he has a peculiar condition where his entire body is an erogenous zone. He has been living while hiding it as best he can. During a summer vacation spent at a relative's house, he meets a mysterious person named Kouda Serio - a beautiful girl with pale long hair, who seems to be his cousin, but he has no memory of her. That angers her and she aggressively attacks him with an "electric massage", which makes him realize that she knows about his secret condition. As they continue to live together, with her constantly teasing his pleasurable places, he begins to fall for her.