@Jkoplo Probably because this one doesn't have any ostensibly sexy female MC people can latch on, like Uzaki-chan or Takizawa-san or some other.
Mind you, I love Uzaki-chan because her and Sakurai have amazing comedic chemistry and she's a riot all around, but do you think they care about any of that?
Anyway, it's weird to rant about that in another manga's comment section, so I'll stop.
I'm glad they didn't keep the "I have to act like a perfect older sister for my sister's friend!" bit. For me, that kind of thing is just annoying and adds unnecessary tension.