Kyosei Tensei

Anezaki Satoru, driven by vengeance after his friend Ichinose Yuna was killed by rapists, brutally killed fifteen men and removed their genitals before being executed. Upon death, he awakens in a world where all men have become mindless, beast-like creatures. Navigating this new reality, he encounters survivors resisting the hordes of these beasts. He discovers that Yuna appears to be alive in this world. Determined to find her, Satoru joins the survivors in their struggle.