I've been seeing this reaction image on /b/ and /jp/ but i can't find the source.
That's Ange Ushiromiya from Umineko No Naku Koro Ni.
Here's a link to the Danbooru pool with all of those. Fair warning, they are a lot more enjoyable if you have actually read the Umineko no Naku Koro ni visual novel (which is in English).
Rifyu is pretty brilliant. Creator of such classic lines as "What a coincidence, it's masturbation time for me too!"