![1girl ahoge aqua_swimsuit black_bow blonde_hair blush bow breasts fate/grand_order fate_(series) front_zipper_swimsuit hair_between_eyes hair_bow highres kilye_4421 koha-ace looking_at_viewer meme_attire okita_souji_(fate) okita_souji_(fate)_(all) one-piece_swimsuit short_hair smile solo swimsuit v yellow_eyes rating:s score:11 post #3752508](/cdn_image/preview/0c/c4/0cc43269e8022c8632ba85eb2e75b947.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).