Nazo no Onnanoko

This girl makes a surprise appearance at the very end of episode 12, the final episode of the anime. Having heard rumors about the mahjong parlor 'Pon no Michi' run by protagonist Jippansha Riko, she travels there to see it for herself. Despite her minimal screen time and completely unknown background, the distinctive aura she exudes and the timing of her appearance at the story's conclusion have sparked enthusiastic speculation among viewers about the possibility of a sequel, with many regarding her as a pivotal character who plants a significant narrative hook.