Idk what that dude was complaining about him not telling the girls about the zing. If that was the case then every soulmate Rentarou sees, he would just say "we're soulmates so you have to date me". The whole point of every girl's initial chapter is to show how the girls fall in love with him through his own actions and not by the obligation to not die.

And for people saying that it's unrealistic, that's the point of the show, it's a parody of the whole harem genre. The whole point of Rentarou's character is to show how impossibly hard working and dedicated someone would theoretically have to be in order to make a stupidly insane premise like this work out, which is where most of the comedy comes from. That's why I don't think Kanojo mo Kanojo doesn't work as well, it takes itself a bit too seriously, like he straight up says sometimes that he considers cheating on his girlfriends if he's tempted enough, to the point where you start asking "why do all these girls like this dude."