After getting exiled by the Lunarians, Kaguya and Eirin got adapted to their new life in Gensokyo pretty quick, but Kaguya never beat the feeling of living without her little brother, neither did him, who missed her a lot every day and always remembered how the Lunarians made her leave the Lunar Capital. He decided to try and end the Lunarians but soon realized it was a really bad idea doing it by himself, so he asked help of the Watatsuki sisters who instead of helping him take 'revenge', Toyohime sent him into Gensokyo with his sister and allowing them to reunite. Mokou didn't know about Kaguya's brother, which then was a big surprise when they met in the forest of the lost after he decided to explore in Gensokyo Kaguya Houraisan & Fujiwara No Mokou x Brother of Kaguya Reader, also i don't own any images in the content