Crossover fan art featuring Misaka Mikoto – character from A Certain Scientific Railgun – in a costume from the Attack on Titan series.
A Certain Scientific Railgun manga began serialisation in April 2007. The anime first aired in October 2009, followed by a sequel in April 2013.
The Railgun is a spin-off of A Certain Magical Index light novel series though. Hence, the Misaka Mikoto character appeared as early as 2004.
Meanwhile, Attack on Titan started as a manga in August 2009 and adapted into anime in April 2013. The anime became a huge hit.
