Hyokai said: Thats it? Mokou wanted Kaguya as her mother/stepmother?
To be specific, Mokou's father was one of the men Kaguya sent on an impossible request (I like to assume it was the Fire Rat's Robe just for irony). Her father, obviously, failed, shaming the Fujiwara clan. Keep in mind that honor and family name were huge in feudal Japan, as evidenced by the practice of seppuku, which Lord Fujiwara may or may not have done.
The reason Mokou probably never dropped the grudge is also probably at least partially due to the fact that Kaguya was indirectly responsible for Mokou's accursed immortality twice over.
1) Mokou drank the elixir because Kaguya spurned her father and presumably damaged the name of Fujiwara. 2) Kaguya's the reason the elixir exists in the first place. It was a joint effort between her and Eirin, and the latter probably would've never tried to make it if the former didn't want it.
Wriggle Nightbug!The cheerful forgotten umbrella, Tatara Kogasa!Two contestants are entering while glaring at each other! It's the fireworks sparked by an eternal grudge!The embodiment of Hourai, Fujiwara no Mokou!Drawing out an endless flickering cloud of insects... a bug of light wriggling in the dark,Behold the limits of forgotten and discarded items!The Sinner of the Eternal and Instantaneous, Houraisan Kaguya!
