Shōnen

From the same author of Hell's Paradise: Jigokuraku

In a world entirely ruled by man-eating titans, the human race has surrounded its residential zones with immense walls, which both prevent their freedom outside the walls and protect them from incursions. However, as a result of the appearance of abnormal titans, who cross supposedly impenetrable  walls, a desperate struggle begins and the young heroes, having lost family, fight the titans alongside the survey corps, with the goal of regaining their freedom.

A man, unhappy with the work he has had to do in life, is involved in an unexpected event ...!
He becomes a Kaijuu, a monstrous creature, giving him a new chance to achieve what he always dreamed of!