I don't see the reason they hate on Kirishima. Although it does bother me that the ML is sleeping around despite claiming to love the FL, it also doesn't make sense that he'd remain abstinent for a girl who doesn't even consider him as a boyfriend candidate yet.
That’s kind of the point. The problem is that he does this with multiple women and yet proclaims his “love” to her multiple times. Additionally, he just doesn’t care about others in a way that is deep and meaningful. If Yoshino makes one small move that he doesn’t like, he could drop her faster than a raindrop. He’s unpredictable.
Okay not gonna lie, every time I see kirishima sleeping around I’m like: “ew, gross. Get this off my screen.” But the reason why I’m not as bothered by the fact that he does so, is because yoshino looks like she has absolutely no feelings whatsoever towards him (as of now). So I’m like: “whatever, as long as my girl isn’t hurt, I’m chill.” Plus yoshino already (sadly) seems used to this type of behavior with the guys around her. (Kirishima, shouma, and even her grandfather) It’s nothing new to her, if anything I’d be more surprising to find a loyal and faithful yakuza dude.