![1girl ahoge ass back black_bow black_legwear black_panties blonde_hair bow breasts fate/grand_order fate_(series) from_behind grey_background hair_bow highres iriehana koha-ace medium_hair motion_blur motion_lines okita_souji_(fate) okita_souji_(fate)_(all) panties pulled_by_self quick_shirt shirt shirt_lift simple_background solo squatting stirrup_legwear t-shirt thighhighs toeless_legwear underwear rating:q score:35 post #3632019](/cdn_image/preview/97/1b/971b684bf0d1c1ff9e032e0e1a4f11bb.jpg)
From http://typemoon.wikia.com/wiki/Koha-Ace (more info there)
Koha-Ace (コハエース) is a parody manga by Keikenchi. It stars Kohaku and features characters from various TYPE-MOON series. It is drawn in a super deformed style, and it is a self-aware series that constantly breaks the fourth wall. Carnival Phantasm included segments based on the series, and it was the focus of the 2012 April Fools' Day joke.
This tag implicates fate_(series) (learn more).