@beperov
I love stories with fantastical elements, but CHARACTERS -- even supernatural, fantastical ones -- have to be grounded in reality. Nasa is a human, he should act like a human. If Nasa does not act like a human, then it's BAD WRITING.
Nasa is NOT acting like a normal human right now. Now, that's not a dealbreaker. There could be any number of reasons why a character would do something abnormal -- but a good writer would have a reason, and that reason would be part of the story.
For example, Nasa is a healthy adult male, but has apparently no sex drive.
He could be impotent and incapable of getting an erection. He could be gay. He could find his wife ugly. He could have taken a vow of abstinence, like a priest or monk. He could be an alien, and have either an abnormal physiology or grew up in an alien culture. He could be a ghost. These are all realistic ways in which a healthy adult male would be uninterested in sex, but if it's the case, the author must TELL THE READER, or at least give us some reason to believe there's a reason why Nasa does not act like a healthy, human male.
But Nasa's seeming ambivalence to fucking his wife is completely unexplained. Nasa isn't an idiot. He has parents, they're still alive, and he grew up with them. He knows how a married couple acts. He knows what married couples do. His disinterest in sex goes completely unexplained, though. That makes his character NOT REALISTIC and UNREALISTIC characters are BAD WRITING.
Now, on the other hand Tsukasa's character is MUCH more mysterious. The author has hinted multiple times at her supernatural abilities and background. She could be a normal, 16-17 year old human. She could be a 1,500 year old immortal. She could be a moon princess. She could be an alien. We don't know, but the author has at least given us those as possibilities, so we have some basis to at least go "Well, Tsukasa doesn't seem that interested in sex either, but the author has given us a plausible reason why that might be."
Well-written characters - even supernatural ones, even fantastical ones - are still grounded in reality.