Saitoo

The protagonist, who was left behind by his wife and his then-kindergartner daughter back when he was still an unemployed scumbag.

Right now, he turned over a new leaf and is now a competent working-adult, but still a scumbag who loves having sex with young women.

He's currently engrossed in "toilet prostitution", but lately he feels that one of the girls he bought might be his own daughter...