Stage 5 boss, a being of half-human and half-phantom. She's both the second gardener for the Saigyouji clan and the guardian of their mistress. The ability is swordfighting.
Youmu arranges the garden with two swords: Roukan-ken is a longer sword that has the power of killing ten ghosts; Hakurou-ken is a shorter one that can slash the human's confusion.
Konpaku Youki, the former gardener, had been the one for about 300 years, but suddenly became a hermit after having made a very young Youmu be his successor. Youmu's swordfighting ability is still in progress, so she needs daily practice. Though Youmu herself has no clue where her master is, she recognizes it by a lesson from him.
This time, following the order the mistress of Saigyouji gave her, she has gathered all of spring essences in Gensokyo to make Saigyou Ayakashi bloom fully.
Here in Hakugyokurou, there are so many cherry blossoms besides Saigyou Ayakashi, which has never bloomed. The former gardener said, "I've seen the fully-bloomed Saigyou Ayakashi before, but this might be the last time." At that time, Youmu had no idea what he meant and why the mistress of Saigyouji gave her an order.
Youmu sweeps the garden of the Saigyouji family; it's about 200 yojanas long (The mistress exaggerates, of course). This garden has a large amount of cherry trees, where is a good site for residents all over the Netherworld. When spring comes, Youmu is very busy in sweeping.
- (Note: Yojana is a unit of the distance that ancient India's imperial army could move per day. 1 yojana equals about 10-15 km. In other words, the Saigyouji's garden is about 2,000-3,000 km. long... Is that so?)
This year isn't the exception, too. The ghosts are really thrilled by the wonderful cherry trees. Everyone said, "I'm happy to be a ghost!" On the other hand, Youmu, the half-human saw this raving scene and got a half sympathy, "I'm half happy to be a half phantom!"
Now, all she should do is wait for the blooming of Saigyou Ayakashi.