Orenowakuchindakegazombieshitasekaiwosukueru Free [new] · Quick

His apocalyptic peace is shattered when a mysterious female survivor named bursts into his home. To save humanity, Sunny injects Yui with an experimental, one-of-a-kind biological vaccine. However, the vaccine functions with a bizarre catch: the antibodies can only be synthesized and transferred to infected girls through physical intimacy.

The twist: Over-vaccination (too many "treatments") can make a survivor dependent or cause mutations. The free version typically limits you to the first area (an abandoned school) and 2-3 heroines. orenowakuchindakegazombieshitasekaiwosukueru free