From SuBLime: 82k2k

Volumes 1&2:
In the immediate family of the story's protagonist everyone seems to die early, and other relatives talk about a curse. When soon after his grandfather's death he comes down with an incurable disease, and is overwhelmed by grief and loneliness, in desperation he re his grandfather's last words -- that somebody was watching over them. He can only find an odd fossil tooth where his grandfather had pointed, but when he picks it up and accidentally gets some of his blood on it, that summons a guardian spirit, who promises to cure him. Maybe he should be pleased, but said guardian has some strange methods for healing.

Volumes 3-7:
Tsumugi Shirota is your typical high school student. He’s handsome, kind, and for some strange reason, surprisingly adept at household chores. On his 16th birthday, a rather unusual but special guest comes to meet him—Master Kurayori, the guardian deity of the Shirota household. Imagine Tsumugi’s surprise when he finds out this deity is also his fiancé!

Included side-stories:
Konoyo Tengoku – director Keiichiro & clerk Tetsu.

Included oneshots:
Nylon Vinyl – an introverted student falls for his teacher.
The God's Don't Exist – a servant runs away from his perverted master and gets help from an aloof engraver.