Incest

I thought he just called his dad's best friend uncle tho

Akifumi's sister married his unrequited love. Yuta is the son of Akifumi's sister and unrequited love.

Incest is only a problem in case of pregnancy, and there's no big chance of that between two guys. And even then, it's a genetic problem rather than a moral one. I'd hardly call it incest, in that case.

Exactly! Since reproduction isn't involved, I think it's fine for them to screw on. Morality isn't an issue here according to my opinion.But the term IS incest though. Sexual relationship between maternal uncle and nephew. Fuckin taboo.

I don't believe in taboos. I use the term "fuck" extremely rarely, but in this exceptional case I would wholeheartily say: fuck all taboos! They have caused more useless suffering to Humanity than any war ever did. As far as I'm concerned, each case should be looked upon separately, and dissapproved only when someone is being harmed. But only then. When no one is harmed in any way, taboos should be immediately abolished.
Aside from that, this is manga, literature; and by definition fantasy. So even if these paper "people" get harmed, it still is perfectly allright, since paper people aren't real.
The term 'incest' is used in the Penal Code of several countries to name a criminal action; that's why I'm reluctant to use it even if technically it would be correct.
The only really bad thing is, if you ask me, inbreeding; when people who are blood-related have children together and pass bad genes in double on to them, thus risking them to have serious health problems, the way many noble families did in the past. In that case, the children are the ones who are harmed innocently.
That's bad. Besides that: as far as I'm the judge, anything goes! Especially for paper people... ╮(￣▽￣)╭

Uh huh. I think the same. Good point well made,bud. Since this is fiction and I'm the reader, I'll judge and assume whatever I want, yes. And inbreeding omfg it really is simply disgusting. Wrong turn made me despise inbreeding even though with my mindset, it could've been overlooked. No matter how pure or beautiful it appears, inbreeding shouldn't be encouraged. Regarding taboo, fuck it indeed. Fuck society and its judgemental people. Being true to oneself and not being hypocritical is the best policy. (づ￣ ³￣)づ

Uh huh. I think the same. Good point well made, bud. Since this is fiction and I'm the reader, I'll judge and assume whatever I want, yes. And inbreeding omfg it really is simply disgusting. Wrong turn made me despise inbreeding even though with my mindset, it could've been overlooked. No matter how pure or beautiful it appears, inbreeding shouldn't be encouraged. Regarding taboo, fuck it indeed. Fuck society and its judgemental people. Being true to oneself and not being hypocritical is the best policy. (づ￣ ³￣)づ

Nowadays, inbreeding isn't that common among people anymore: even if 2 blood-related people want to have sex, they will be taking precautions in order to prevent pregnancy.
It is mainly a problem for domestic animals: dogs and cats. All those serious health problems among dog breeds like hip dysplasia and so, all are caused by the breeders wanting to "create" new breeds or exaggerate typical features in order to win prizes, like the extreme flat noses in Persian cats, the bulging eyes in Pekinese and other dogs of that type, and of course the huge dogs who risk having to be put down before their time because their bones are overstretched. There should be a strict law forbidding that. It causes LOTS of pain and suffering!
For people, in former centuries, nobility used to wed their children to close nephews and nieces to keep the property into the family, and also because there weren't all that many candidates to choose from for them, as there were for common people: a prince couldn't possibly wed his kid to someone who wasn't a princess or a prince himself, that wasn't allowed. So they had no choice, really. They knew very well it caused health problems, but they accepted that as an unavoidable and necessary evil. So they weren't really mean, just didn't have much of a choice, grades and statures being so strict in that time.
As for isolated groups of people in remote provinces of large countries, the inbreeding is mainly caused by ignorance, and also lack of choice. (I'm thinking "Deliverance", right now... )
And finally there are these religious communities like the Fundamentalist Church of Latter Day Saints, who practice polygamy, keeping the weddings into the community so closely they have caused a huge epidemic of a very serious disease called Fumarase Deficiency Syndrome as a consequence of their inbreeding during several generations. That's one of the many dreadful effects of fanatic religiosity.
But inbreeding and incest aren't really the same thing, the terms shouldn't be confused.