Honestly it's highly likely gonna be yuri and yaoi integrated, so it's better for you to stop reading after ch 1 because it's surely gonna be yaoi with the guy that goes to Tokyo probably being with another guy.
I genuinely just recommend reading "Cocoon Entwined", it's by the same author and though it's not about zombies, it has that same eerie-like story that makes you want to read more!
Plus it's Yuri only too because it's set in a girls-only school!
I get not wanting to read BL, but what are you disappointed for? The author can write whatever they want and can venture into any genre they desire. Just don't read instead of commenting about how you're disappointed it's not yuri yall all about representation and inclusion until queer stories feature BL too. Yuri and Yaoi are both queer ://
If you already noticed the yaoi tag, what's the point of the "disappointing" comment? I prefer BL. I've been reading it for more than 10 years now. But I rejoice whenever I see yaoi and yuri together because even when I prefer BL, I like queer stories in general. Especially this story, it seems like it's gonna be a good story with a rich plot line, so if you're only against this cause there's gonna be two guys in a relationship, then it seems kinda gayphobic ngl.

Probably gonna get downvoted by a bunch of people for saying this, but someone PLEASE DM ME the list of chapters of ONLY YURI/GL when this gets completed, not wasting my time on waiting for new chapters just to be disappointed with yaoi/BL.