Kasen Ibaraki is a one-armed horned hermit. She has passed through the Great Hakurei Barrier to the outside world many times. She has never told her friends in Gensokyo her reason for going to the outside world, and the mystery only deepens.

Kasen always seems to be single-mindedly searching for something in the outside world. What could it be...? Once, Sumireko spotted her in the outside world going into a certain store...

Besides Yukari, Kasen is probably the person most knowledgeable about the outside inside Gensokyo. Kasen is friends with Sumireko, who often goes to play in the outside world, and she herself also heads to the outside fairly often.

Kasen is thought to be one of the leading gourmets in Gensokyo, but hermits do not need to eat like normal humans. For Kasen to still be so fixated on food, well... She must be quite the glutton.

There is a theory about why Kasen likes to eat in the outside world so much. Within Gensokyo, she has to follow the way of the hermit, but when she is in the outside world, she can eat whatever she wants. However, there is no way to know whether this is true or not without asking the hermit herself...