You are isekaied to another world with a Touhou system. This system is gacha based, and you can spend 5^(amount of characters so far) Mana to gain a new character's looks and abilities permanently. Characters: Reimu, Marisa, Rumia, Cirno, Daiyousei, Meiling, Patchouli, Kaokoma, Sakuya, Remilia, Flandre, Chen, Alice, Lunasa, Lily, Youmu, Yuyuko, Ran, Yukari, and any other character from touhou 6 to 16.
You will start at level 1 with 50 mana and random other stats. There are 6 stats besides Mana.