From Echochi Scans:

Itou Katsuya has been living with his guardian, a young man named Tooru, after the death of his only parent - his mother. Katsuya is having problems recalling the incident and can’t even remember how she died in the first place. To makes matters worse for poor Katsuya, he harbours conflicting feelings that are beyond what a son would normally feel for a father. Thus, life with Tooru during his puberty is pure torture.

Then one day he met a man who claimed to be his deceased mother's old friend. He was told that his mother perished in a hit-and-run accident and that even now the culprit hadn’t been caught yet. Katsuya embarks on a journey to find the killer while battling his sinful feelings for his foster father, Tooru...