Me~teru no Kimochi [Manga]

Koizumi Shintarou is a 30 year old who has been isolated in his room for 15 years. His father, who he blames for his condition, brings him food and manga to read, and tries to encourage him to come out, without success.

When his father gets married, to an extremely beautiful woman, and then soon dies afterward from cancer, the hermit is left to deal with a woman younger than he is, whom he is very attracted to, living in his home, and taking care of him.