Mou Tamago wa Korosanai

From MangaHelpers: This is a collection of 4 short stories. One story tells of the ghost of a pretty girl who died too young. She has unfinished business, particularly with the boy she likes, and she's willing to possess someone to deal with it. Another features a girl who is hosting a genius boy in her home, where she lived alone. She was looking forward to his arrival, but he seems to be unexpectedly unsociable and unfriendly. Is there some way the relationship between them can grow?