I… have no idea! My first thought was novel art, but when I image searched it, I just found a lot of doujinshi with Asch and Luke in frilly pink lingerie. Clearly google images is not going to be helpful there. (Either that, or Asch and Luke wearing frilly pink lingerie happens in the novels, but somehow I doubt that.)

…Now I'm really curious, though.

NO WAIT I TRIED ZEROCHAN AND FOUND IT. The answer is Luke. Luke is what's wrong with Asch's mouth. Clearly. Luke is what's wrong with Asch, period.

♥ ♥ And thank you, uwah.