Donmai

Series: Touhou - Nanokagetsu Sakuya (Futatsuki Hisame)

Original title: 七日月咲夜
Artist: Futatsuki Hisame

The title is a play on Izayoi Sakuya's name and Japanese names for phases of the moon[1].

Nanokagetsu (七日月) is the 7th day of the lunar phase, i.e. the first quarter moon.
Izayoi (十六夜) refers to the 16th day -- the first day of the waning moon after the full moon.

This might also have something to do with Sakuya being a child in the comic.

[1] Wikipedia(JP): Moon#Names of Lunar Periods

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