I get that these type of characters exist for the purpose of serving as a contrast or advancing a theme of the story, but holy god are they disgusting and uncomfortable to read about. I've yet to meet anyone like them in real life, even among all the guys and gals I've known who get way thirsty and among those who've cheated on a partner or tried to keep a number of casual partners in the past. The very idea of taking someone in in need of a home just for sexual exploitation and then throwing them out, not for poor behavior or trashing the house but simply because it could inconvenience you and your other sexual escapades, makes me angry and a bit sick to my stomach.
Surely there was another way to write in a character representative of Sayu's troubled life as a runaway without having it be such a disgusting, irresponsible, self-centered fuckwit.
The sooner the author writes this guy back out of the story or in front of a moving train, the better. A redemption arc for a character like his in a story about growing up and facing down your mistakes and challenges would take up way too many chapters and involve way more support and charity than this guy deserves. Would infinitely prefer the story stick with the complex and selfish characters we've already got, who at least all are trying to do the right thing and are thinking about others' wellbeings to some extent.