This might be one of the most overrated stuff that i had (dis?)pleasure wasting time on. Mainly because my suspension of disbelief shattered after first two or three chapters. Everybody knows what happens to people like Machida in "real life" - they get bullied, extorted and taken advantage of (similar, but different case to "Yugami-kun", who would've had shit beaten out of on regular basis by his peers, probably since kindergarten).
And the reason behind Machida's perceived pureness? He has little to no personality, and that emptiness is creepy. He's perfect stoic (trope, not philosophy school, even if they may overlap heavily) with no passions whatsoever, accepting everything that comes his way. I understand that this manga is iyashikei, and if it does "heal" you in some aspect, or help you in bearing with hardships of everyday life, good for you, but those ratings and award nominations (!) seem like a joke made in poor taste.
Average at it's best, absolutely unbearable at it's worst (and i actually plowed through Yesterday wo Utatte - and liked it -_- ).