And here's proof: footage from Tudou of Attack on Titan cosplayers reenacting Shinhwa's music video for the song 'This Love.'' Or, more plainly, the characters of Attack on Titan pretending they're in a South Korean boy band.
Why this song? Probably because someone mashed the anime with that song already in this kind of amazing, kind of hilarious video:
Not only is Armin the love interest, but I think Erwin could probably give a lot of real K-Pop stars a run for their money.
And here's the original music video, if you'd like to compare:
This love [Shinhwa] Shingeki no Kyojin COSPLAY ver [tryingtobeopenminded via Elliot Trinidad]