@Throbelisk To explain what I was saying, if their moms were to marry and be in a relationship then by the law they're both siblings. It is counted as pseudo-incest however if Riko and Chika were to pursue a relationship with each other. But I see where you are coming from seeing as if they were consenting adults it wouldn't matter even if there is some form of familial relation, but they're in highschool so it basically throws that entire thing out the window.