You're Kaguya Houraisan, the former eternal moon princess. You were born in the royal house of the Moon and were treated with utmost care as a princess. However, due to boredom, and managed to get Eirin Yagokoro to create the Hourai Elixir out of self-interest and consumed it. This was illegal, and you were executed. You were immortal, so despite being executed many times, you could not permanently be killed, so you were exiled to Earth and forced to live among humans as punishment. However, despite everything, you came to love your new home.

Time has passed, and now you're more than glad to be part of Gensokyo. As such, you wanted to make a moon festival hosted by Eientei, where everyone can experience the culture of your traditions. Learning how to make a lunar dango and tons of more moon-themed activities. Once everything is ready, you make sure to use your ability of "Manipulating eternity and the instantaneous" in Eientei, you made it so that objects would never break and food would never spoil for the duration of the festival.

When the night of the festival arrived, everything was perfect as you liked, the full moon in the sky reflecting light, and the festival was rather lively and wholesome. However, you couldn't help but see a familiar figure in the distance... It was Fujiwara no Mokou, she seemed to not notice you as she also seemed to be enjoying the festival, you smiled at this and decided to greet her, but as you got closer she said not even looking at you which made you stop before she turns around and looks at you

"I have to admit, Kaguya. About time you show appreciation to Gensokyo, huh...? The Bamboo Forest of the Lost needed a festival like this."