Dokushin Kizoku wa Isekai wo Ouka Suru ~Kekkon Shinai Otoko no Yuuga na Ohitori-sama Life~

[Haxens]

There's usually a reasonable amount of isolation that someone does,but this is excessive

 

[razorresidue]

The fact that the description tells you nothing other than the fact the MC doesn't want to get married is, in fact, because that's the only thing the manga is about. There's no plot or goals to speak of and no characters worth paying attention to. I kept at it hoping that maybe someone would have an actual character arc, but there's been no sign of that. For a slice of life that might be fine if the characters were interesting, but they are not. The MC, meanwhile, is a completely insensitive, self absorbed, jackass. Enjoying your me time, not wanting to spend a lot of time with people, and not wanting to get married is completely fine. Not wanting to interact with anyone outside of when you want something from them doesn't sound healthy, but I'm not a therapist. However, giving little to no consideration for anyone else's feelings or desires while being rude and dismissive any time you aren't trying to manipulate them into something sounds like some sociopath shit. And frankly forgetting your own niece's name and feeling no guilt about it despite how much it clearly hurt her should not be something someone looks at and goes "oh yeah I really relate."
I'm not condemning anyone who relates to this MC, because I doubt you are actually like that, but at least consider if this is what you want to present yourself as.

The plot is simply the MC relaxing in his second life, the story never really set up any grand story even in the description so you should know nothing really happens. Magic is mainly used as a backdrop to help the MC create stuff. The characters around the MC have their own goals, mainly the musician, however the MC’s goal is straightforward, and unchanging, which is a refreshing change.
You’re far too harsh on the MC when he has his reasons. The main reason he avoids his family is because they put their expectations on him despite him clearly stating he doesn’t want to do that, and they still pester him. (He even states he’ll apologize to his brother for taking his responsibilities) Why would he go to family reunions if all the questions are “When are you getting married?”
The MC doesn’t go to people when he wants stuff from them, usually its the other way around. Ethan (the character he met camping) had nothing he wanted, and he still shared his meal with him, and ultimately helped him get married despite feeling a kinship with him. His own employee did that after he wasted his money on a girl, and wanted to eat expensive food off his money, yet the MC is insensitive?

He forgot his niece’s name, sue him.