is a Japanese manga series written and illustrated by Wataru Watanabe. It began serialization in the 12th issue of Akita Shoten’s Weekly Shōnen Champion in 2008, and as of March 2019, the series has been compiled into 63 tankōbon volumes. An anime television series adaptation aired from October 2013 to July 2014, followed by a second season aired from October 2014 to March 2015, a third season aired from January to June 2017 and a fourth season aired from January to June 2018. A live-action television drama adaptation aired in August 2016. A live-action film adaptation is set to release in August 2020.