End Game
After his then-boyfriend drives drunk and kills a woman on a bicycle, then flees the scene, Tooru--an artist--becomes unable to work with the guilt of the woman's child with bloody hands crying for his mother in the road. A few years later, he adopts the boy and vows to make up for what happened. As the boy grows up, he falls in love with Tooru and they eventually have a physical relationship, but Tooru is never willing to tie Katsuya down and never says what he feels or wants. It's frustrating because of that, and a little odd since they were technically adopted father and son, but they aren't related and spend long periods apart now that Katsuya is an adult. And I don't believe Tooru ever had any attraction toward Katsuya until he was older and starter pursuing him. A nice story but not really fulfilling to read.
Sekai wa Shippo de Dekiteiru