Free — Orenowakuchindakegazombieshitasekaiwosukueru [upd]

Readers often praise the art style by Gotaro, which manages to be both detailed in its horror and expressive in its comedy. While the premise is definitely for mature audiences, the story's fast-paced humor keeps it from feeling too grim despite the apocalyptic setting.

This description matches the premise of a notorious adult-oriented (R-18) indie game genre in Japan—often referred to as ero-guro or parody RPGs made in RPG Tsukuru (RPG Maker). The most famous game fitting this exact description is (俺のワクチンだけがゾンビした世界を救える), which translates to "Only My Vaccine Can Save a World That Has Become Zombies" —but given the phonetic similarity, "wakuchin" (vaccine) vs. "wakuchin" (slang for penis), the title is an intentional double entendre. orenowakuchindakegazombieshitasekaiwosukueru free

The core mechanic of saving the world via sexual acts places it firmly in the "borderline hentai" or smut category. Readers often praise the art style by Gotaro,

You can find English translations of the manga on several community-driven platforms. These sites typically host fan-translated chapters: The most famous game fitting this exact description

They called them — not mindless, but wrong. They remembered how to open doors, set traps, even speak broken phrases. "Huuungry. Join. Peace." But their eyes were milk-white, and they fed on the living.

It sounds like you're referencing a Japanese phrase: — which translates roughly to "Only my vaccine can save a world that has become zombie" or "In a world turned zombie, only my vaccine can save it."