Yukari Yakumo is a youkai who manipulates boundaries. She uses gaps to appear throughout Gensokyo and leaves Reimu with troublesome tasks to complete before disappearing. She was the first to notice the Seal Crystals. With a smile, she said this was because she loves Gensokyo more than anyone else.

The full moon is opposition. In other words, it is the celestial body that is opposite to the sun when viewed from Earth. When there is no eclipse, it receives the light of the sun to shine round and bright. The full moon is 1900 times more luminous than Venus at its brightest. Since long ago, the pattern on the moon's surface has been said to resemble a rabbit. However, it has also been said to look like other things. Human eyes are so interesting...

An anecdote from more than 1000 years ago: Yukari manipulated the barrier between truth and illusion to jump into the reflection of the moon in a lake. The reflectin led to the moon itself, which she invaded. She brought many arrogant youkai with her, but they were all defeated by the modern-day weaponry of the Lunarians. Since then, Yukari has been more discreet in her actions, having Reimu and her companions build the rocket protected by the three Sumiyoshi gods, which she used to bring about the second Genso-Lunar War...

Toyohime, Yorihime, and Reisen forced out the invaders, including Reimu and Yukari, after receiving Eirin's letter. Meanwhile, Yuyuko accepted the request of Yukari and successfully sneaked into the Lunar Capital with Youmu. They retrieved the 1000-year-old ancient sake, leaving Toyohime and Yorihime speechless.

If the second Genso-Lunar War hadn't been declared a victory without bloodshed... If the strongest oni and Yukari's friends, Yuyuko and Okina, had been brought to the first Genso-Lunar War... the anecdote would definitely be different. It won't be easy to predict the outcome of a third Genso-Lunar War if one ever occurs...