Its actually pretty solid that Igarashi could get her too.
I can't read Japanese, but you can still tell whats going on pretty decently.
They spend a moment on each of the boys: The kouhai's doesn't seem too serious and neither does Nana's. But for Igarashi, hes the first person who realizes he likes her legitimately even when shes FAT. like...she turns fat again and all the guys are really disappointed and it looks like Igarashi is the only one whos like "hmm well shes still her so I still like her" I think he also gets into some of the games she likes. Chapter 17 on is part of Mitsumi sempai's moment.
chp 3.5 pg 15 "Were you too busy riding something else?" oh my fricking god xD