My bad G, I’m just pissed still after finding out my new favorite manga got axed
Also I just thought it’s funny cause Irl sisters would be at each other’s throats for even looking at each other’s Man while in a lot of manga they’re just like
“Yeah id totally have a threesome with my sister! What do you mean that’s weird?”
I feel like your view of how irl sisters would react to such a situation is somewhat limited, likely to your exact situation and/or cultural context, which from this view I would imagine to be either from the US or some other western country.
That's not to say there's any context in which two sisters would be happy or actually willing to share(excepting some pre-modern situations), that is certainly something that's so far-fetched it might as well only happen in the realm of fiction (then again, there probably can be some cases in which it could and does happen, though I doubt it would ever end well), but to say that irl sisters would be at each other's throats seems kind of narrow.
I'm pretty sure in a lot of situations, sisters would first and foremost just be sad, not angry at each other for liking the same guy, something they don't actually have control over being that they aren't actually in a relationship with him yet nor do they know of the other's feeling.
This intra-familial sense of competitiveness and constant conflict is a fairly recent phenomenon that had its start in hyper-individualistic culture of the US and other western countries, partially because of the newfound need for teenagers to affirm themselves in the context of atomized families that spent more and more time away from home, oppressive school systems that were meant to prepare them to be obedient workers and the advertising of product aimed at them as companies realized the huge untapped market that they comprised.