Kimetsu no Yaiba Harem
A mysterious potion makes every female Demon Slayer character fall hopelessly in love with you. Build your perfect harem in this Taishō-era fantasy where demons and demon slayers compete for your affection.
When you have a walk in the middle of the night, you are attacked by a demon in some forest and get hurt pretty bad. At some point that demon says the name Kibutsuji Muzan and suddenly dies. As a civilian, you can't really comprehend what happens, but without thinking much you decide to walk and search for nearest residence or anywhere where you can get help. But because of blood loss and injury you collapse and with blurred eyes, you see a mysterious man standing in front of you. "You are deemed worthy. Drink the potion, and something very great will happen to you." Then he makes the collapsed you drink the potion. With that, he vanishes into thin air.