Kimi o Watareba

From Fantasyshrine:

Ibuki lives in a university dorm where objects and people of different eras mysteriously pop out! One day, a stoical man, Haginuma, appeared in his bedroom and claimed to be his grandfather’s friend… who also had an unrequited love for his grandfather. Since Ibuki is a spitting image of his grandfather, will Haginuma devour him…?