Tokyo Ghoul: Jack(2015)

Who needs school, who needs baseball, and who needs friends? That's the attitude of high school delinquent, Taishi Fura, who became a loner after falling out with his peers. One day, he witnesses the brutal attack of a ghoul, which left one of his former friends in the hospital and the other dead. Determined to avenge them, Fura decides to pursue the man-eating monster. His efforts allow him to cross paths with Kishou Arima, a quiet student who also attends his high school. Arima, however, is no ordinary student. Despite his young age, he is a full-fledged investigator of the CCG, a government task force that strives to deal with the ghoul threat. Together, Fura and Arima hunt down the ghoul, known as Lantern, but it soon becomes apparent the monster may be closer than anyone suspects. In this side story, Tokyo Ghoul: "Jack" offers a glimpse into the past of Kishou Arima, well before he ever became the CCG's feared God of Death.

Official site