Kurumi

The main character meets Kurumi as the guardian of the lake. She said that she has defeated all the intruders who tried to enter the lake (at least up until the events of Lotus Land Story). She was easily defeated by either Reimu Hakurei or Marisa Kirisame. On the third stage of Lotus Land Story, Reimu or Marisa, depending on which character the player is using, entered Mugenkan before the other character. Presumebly, they must have passed Kurumi somehow.