because that's the law we made when we were introduced to anime: for example if we both are interested in one anime, we can watch it. but, if one of us has started watching an anime (and she started watching mha WAAAAAAAAAAAY before me), and the other suddenly wants to watch it, it is up to finder to decide. and my sister decided that i couldn't watch mha, so yeah. also, if one of us quits watching an anime, an the other is interested in it, the interested one can watch it. sorry if it confused you, but that's sirta how our treaty of versailles works (we named it that because we're extremely obsessed with history)