@Kaarme I'm not sure one should take some of these tags too seriously, in connection with this manga.
It has the "Romance" tag as well, and while the two main characters have a close relationship, I don't really think it's particularly romantic. It's more like a "surrogate parent/child" relationship, but I guess there's no tag for that.
@evoliios That would be a nice. A whole lot better than another potential love interest, that's for sure. If she's the dude's sister, I hope her personality is just as good. Not that it would spare him from lectures, I reckon.