The World's Strongest Rearguard: Labyrinth Country's Novice Seeker, Vol. 8 (manga)

Arihito and his party have finally made it to District Seven! In order to give their combat prowess a boost, they decide to open the Black Box they received in the battle with the Vine Puppeteer. But according to Ariadne, a dangerous, sentient weapon—an armament—is sealed within…