That's not buildup, that's foreshadowing. Though how good that foreshadowing was is a different issue, especially considering that that was one day, and there were several other comic days that hinted that croc might be going to commit suicide or go on some kind of murder spree, but those ultimately were red herrings.
Buildup would be if before the final 100th day, there was like a week's worth of comics that hinted towards the idea that he would die in a car accident until it actually happened. But nope, before the final day, it was just croc doing random things with his friends. Thus the final day he died suddenly with zero build up.
he live https://twitter.com/yuukikikuchi/status/1240956772203917312?s=19
*addition : what i find is that link on his twitter i think is the Ending song of this comic from Ikimonogakari even though I still cant watch it (even so many japanese cant watch it)
It's crazy how this author made us attached to this Croc in 100 days...
I'm gonna miss him.
;_;
@kentoiwao
>This video contains content from Sony Music Entertainment (Japan) Inc., who has blocked it in your country on copyright grounds.
God dammit Sony