Yami wo Tsugumono

Dool and Tatsuki are a demon hunters. Living like ordinary people in the daylight, they secretly hunt down demons when they sense them. They find an old lady with a small girl with supernatural power. Tatsuki, as someone who is also a small child and has special powers, relates to the girl and tries to guide her to live happily among the people.

Suddenly they are attacked while talking, but are saved by another mysterious man. Tatsuki tries to get to know him, but finds out the reason that mysterious man has come is to seek revenge for someone he loved and that Tatsuki is the mans target.

Note: There is another story included at the back of the manga called Elnera. It is about a sea demon called Elnera and the love between a human boy and Elnera's daughter.