Quote from mellowmut
well wouldnt incest be like when they are related by blood? well not saying it isnt a bit jacked none the less but theyre not releated <_< you know them crazy japs though..... its ok to marry ur cousin >_>
Incest by definition is crime of sexual intercourse or marriage between persons within the degrees of consanguinity (relationship by blood or by a common ancestor) or affinity wherein marriage is legally forbidden. However in both cases (blood relationship and affinity) each country has its own legal system for these situations and so there is no global rule for this.
And another thing: how this silly manga sprouted this discussion? Fiction is not obligated to follow any moral standards or legal systems, it is fiction after all.