character_request removed. This is clearly either Patchouli or someone cosplaying her. Perhaps someone with a Pixiv account and Japanese skills could check out the original post and find out who it's supposed to be.
No idea where this picture came from, but it doesn't belong to this artist I believe so source might be wrong. Pixix tags パチュリー・ノーレッジ / パチュリー (patchy) + 水着 (swimsuit) / ビキニ (bikini) doesn't brings up this picture anywhere. (Unless I am blind)
it's right at the bottom of the gallery given by the source link
Ah I see. The ribbons, style of hair for alternative and the striped bikini screams Patchouli but often artists/people don't tag all the characters in a multi-char work.
This almost seems like a smug ドヤア / boast from slim Patche but yea difficult to find out.