Ore no Vaccine dake ga Zombie-ka shita Sekai wo Sukueru

Yuu Oikawa, a shut-in at home who is 22 years old, is doomed to die a virgin because the entire world has turned into a place overflowing with zombies… until one survivor shows up at his house. That woman, who calls herself Sunny, injects Yuu with a vaccine that has the potential to save the zombified world…but as a result, Yuu gains the power to revert zombies back into humans through sex—?

(Source: Kurage Bunch, translated)