
There is many manga and anime that have a girl that likes to dress as a dude. They like the uniform or like the flexibility of the uniform.
I only think the person is female just because she does mention that the main lead only sees guys and that is why she never paid attention to the unknown person ( implying that they may be female). Another is when the dudes killed the unknown person and said " some bitches got here first " or somthing like that ( true the word bitch can also be used for a guy). Having said that, I don't mind if the unknown person is female or male, love is love.
I agree that she will not fell in love right away, i think the author will develop the love as they try to survive this zombie world. I can feel that this is going to be the best horror/ romance manga i read in a while, if ya want to check another horror romance i would recommend this one : Glotoneria.
The Only good Yuri I have seen was romance revolution and my maid is a dragon. For some reason I have not seen many good Yuri that had interesting stories, but when I find one! Oof it stays in my heart