Akito Narusawa 
Finding Avalon: The Quest of a Chaosbringer Volume 5 [EPUB ebook] 

In the aftermath of the Battle of the Classes, Piggy hopes for a little respite, but he’s in for a disappointment. Tsukijima, Piggy’s hotheaded classmate and former player of Dungeon Explorer Chronicle, finds it insufferable when the many bullies of Adventurers’ High once again target the lowly students of Class E.

Piggy goes into panic mode when Tsukijima’s violent retribution leads to a duel between Tsukijima and Ashikaga, a powerful student and member of the nobility. If Tsukijima exploits his game knowledge to easily win this clash, it could have significant consequences. Everything could spiral out of control if this world isn’t steered in the path of the game’s good ending.

Now that he deeply cares for Piggy’s family and Kaoru (his childhood friend), the player inhabiting his body must also use his “cheats” to keep Tsukijima in check before it’s too late.