Although I don't know what happens after the divorce with MC's ex, he didn't know that the MC was the SSS ranker, he was just told that he was an adventurer that hasn't improved his rank in a long time by MC's ex. He assumes that he's a low ranking adventurer due to this misunderstanding.
Let me give you some background, he was a guy with a good record on track to be promoted soon with a salary that was already 400,000 yen per month. He was introduced to MC's ex by one of her friends that also work in the guild, cause the friend is trying to convince her to leave the MC. MC's ex wasn't convinced, but was on edge enough that if a big push was made, he would get her. His boss, who heard of the situation, decided to give the NTR guy permission to delete the MC's card to strong-arm the MC's ex to him.
How he gets caught: days after deleting MC's card, heads of the adventurer's guild come in his adventuer's branch--knowing that the MC's card was deleted there, and find out that only the NTR guy could've done it during the time frame. He finds out the MC's identity because of it and goes into shock, then he's placed under house arrest as he thinks how things went wrong. After the house arrest, his boss (who recommended the deletion, but seemingly got no punishment) acts like a stranger to him, and tells him his punishment. His salary is cut in half and relocated to another branch, since the MC told them to keep the punishment light. NTR guy decides to hide his punishment from the MC's ex (now his wife), and now lives with her--living off his savings and hoping his wife gets a job to not face financial trouble.
His life with MC's ex: it goes terribly. The adventurers branch he workers at is 1 hour and 30 minutes by rail transit, and he doesn't actually work: the branch is just filled with people the adventurer's guild wants to get rid of, so they just check-in and leave. It sounds great, but for the NTR guy--who had many talents and was on track for promotion, frustrates him as he sips coffee from the vending machine. His wife (MC's ex) is also terrible: can't cook (eventually just uses instant food instead), can't get a job (look at my other comment why), and just spends money to look prettier (that's now tapping into his savings); the only saving grace for him was that she was pretty. Because she keeps trying to get a job and failing, he suspects her of something, she says she has no friend where they live, AKA their first couple fighting. He gets frustrated and confides his problems to a woman at work, who also has problems with her family. They begin meeting often to the point he eventually sleeps with her; afterwards, he finds out his wife was hospitalized and now had a scar on her face. He's finally convinced, with her no longer looking pretty; on her hospital bed, he declares a divorce and leaves her.
And that's all that I've read. I've skimmed so I don't know the full story, but that's the last I saw of him for the first arc. If someone knows more, please tell me; the MC is the most boring part of the story, I actually like his ex (who two-timed) more than him lol
Like seriously, the MC is so bland and boring, and he always doesn't want to communicate the full truth--which leads to the events in the story. It's said in the story he was more intelligent due to absorbing magic stones at a young age, which is suppose to be dangerous for those under 16. So I don't know if it's actually implied, but instead of intelligence, I think he got brain damage from absorbing the magic stones. In this type of story, you're supposed to be rooting for the MC, but I'm rooting for his ex instead, since she's more compelling and grows from her mistakes.
But yeah, NTR guy thought he was Netori guy, not Netorare guy.
