probably not it might just be some fanart but it also could be an actual manga i searched it up and the only thing im getting is this: Shingeki no Kyojin dj - Heichou de Moushouchuu Manga i found it on manga fox
hope i helped you (=・ω・=)
Yeah.. It's just art by Watanabe Asia.
I like it much as well, even tried to find an ori pic but non..
How about reading her other works..
http://www.mangago.me/r/l_search/?name=Watanabe+Asia
http://iweb9.mangapicgallery.com/r/newpiclink/love_mission/5/5cbaa0a4f888fe9a52ca945e1380fe2b.jpeg