Devil's advocate, benefit of the doubt and all that:
Karen and Kazukage are childhood friends. Karen's the victim of an abusive household and MC maybe doesn't realise why she's always reluctant to leave, but recognises it and has no problem with it, being the older one. He enters middle school, maybe moves, maybe Karen moves, but loses contact with Karen.
Big Time skip.
Kazukage moves from small time to big town for high school or university, loses most of his long-time social circle of friends in home town and can't quite make a connection with big town people. All relationships are on an acquaintance and associate level. Enter wife. She's sociable, like Kazukage (and/or his income doesn't hurt), they marry. He finally makes friends via her. The usual merger of social circle of husband and wife is more like he got anschluss'd to her circle of friends. He's acknowledges as the big, but quiet guy.
They build a house.
Wife either gets a side piece or is disillusioned with her married life. But she likes the house. Side piece or "friends" talk and maybe convince her to leave him. But she likes having a house. So since he's a big guy with no friends of his own, well domestic violence wouldn't be particularly surprising, stereotypically speaking. And she might get the house, right?
Recording of "suspicious" audio. Divorce claiming domestic abuse, verbal and physical. Settlement to the tune of 2 M Yen, 13-14k USD.
We don't know if ex-wife getting the house instead of the settlement was on the table, but doesn't seem unlikely.
Anyway, Kazukage sells house to settle (which still leaves him in crippling debt, since he paid for the house, this being Japan, or at the very least his name is on the contract, and a loan is a loan is a loan, come high water or broken bone. That's why he's currently in debt, having to pay interest, look for a place to stay, save up on first rent at least (prolly, don't know the sitch in moon country), and still stay somewhere in the meanwhile. Net cafes are only a stop gap solution for that.
Come present.
We don't know how much time passed between him being presented with divorce papers and the current events, but it's somewhat safe to assume that he wasn't allowed to stay in his home while the proceedings were taking place; courts traditionally take the wife's position in these kinds of events, and if Japan is anything, then it's traditional.
Furthermore since his friend circle in this scenario is in his home town, he's been ostracised on the word of his ex-wife, whom most/all know better than him.
Furthermost: Japan doesn't have "innocent until proven guilty", it has the opposite, "presumed guilty until proven innocent". Her wife claiming he verbally and physically assaulted her puts the onus on him to prove he didn't, which is very hard to do. Combine that with their whole "don't rock the boat' shtick and their prejudice against any who stand out, and you arrive at Kazukage's position, where he's presumed guilty, can't prove his innocence, can't call on character witnesses - he would need to tell them why he would their statement, which would both inconvenience them and sully his reputation in his hometown, since he's presumed guilty until proven innocent!
Well, so now all he's left with is his former next-door neighbour to spoil him rotten. Wait, no, that's a different...