Astral Online: Maou no Noroi de Saikyou Bishoujo ni Natta Ore, Saijakushoku da ga Cheat Skill de Chou Seichou shite Musou suru

Sora Kamijou, a high school boy who is addicted to VR games, starts playing Astral Online, a VRMMO that has been talked about as a god game, and suddenly finds himself fighting against the Demon King, the last boss. In addition to the sudden battle, the Demon King casts a curse on him and transforms him into a beautiful silver-haired girl...? A new VRMMO fantasy involving both the game and reality begins!

(Source: Kadokawa, translated)