Based on a poem called "Fujimi Saigyou" by Saigyou Houshi.
I wasn't able to find the poem, but "Fujimi Saigyou" seems to be a common subject in Japanese art, particularly in paintings depicting Saigyou Houshi in traveller's attire gazing at Mt. Fuji.Hu~m...So these are the kind of clothes girls these days wear~"Girls" is written with the same kanji that was used for "daughter" above.Yuyuko-sama trying out a uniform
The 23rd of February is
Fujimi('s Daughter) Day!
Since Yuyuko is called Fujimi's daughter in derivative works, this day is considered as Yuyuko's day
I might be misinterpreting what the artist wrote, but the phrasing 二次創作 seems to imply this is done in fanworks, while it is stated in Touhou canon that Yuyuko is "Fujimi's daughter".
Either way, the date is a pun:
Fujimi → fu(2) ji(as in second or next; 2) mi(3).
The commemorative day was apparently created by Fujimi town, in Nagano. The town itself was named after the fact that Mt. Fuji can be seen from there (Fujimi literally meaning "Fuji view").
