Debusen S01 E06 Episode 6

Keiko kidnaps 6 of Mitsuru's students. Mitsuru rescues them. Keiko and he go to the woods. She puts on a mask, and attacks him, but by giving control to Mitsuko, they defeat Keiko. He finds Mitsuko's skeleton, and gives back the ring, becoming himself again. His students cry thinking Mitsuko is dead, but when Mitsuru pops up, they chase him. He becomes a nun, but the churchgoers turn out to be his students as wild as ever.