Sweet Home (KAYAMA Yumi)

From Jigoku:

Katsuhiko and Youji enjoyed their life of living together. Suddenly, Youta, Youji’s son, came to visit and stayed with them. Katsuhiko’s not happy about it at first; then eventually he saw himself through Youta, a child who’s grieved over his parents’ divorce…

Besides the main story, this book also enclosed two stories about Katsuhiko’s past relationship with other men.