Mob Shoujo ga Last Boss Majo wo Shiawase ni Suru made

Story

"I want to see your smile again" — A new girls' fantasy! A girl remembers. That this is a game world. That she had been reincarnated as a mob character. That her best friend would one day become a witch who freezes the world. And — that she would become the final boss and be destroyed. "I promise, I won't let Grace become a bad person." She refuses to accept such an ending! The girl Roselika makes her resolve and takes the hand of her best friend Grace, who has manifested the supernatural power that will turn her into a witch.

Synopsis via AniList (English).