The Hero Is Overpowered But Overly Cautious Novel Vol. 7 (novel)

Feeling ill-prepared for the looming battle against Mash the Dragon King,Seiya returns to the underworld to acquire some new skills. But every boon gained from this dark realm comes at a cost. While Seiya practices a stealth ability, Rista turns invisible! Ashe hones the power of darkness, disaster strikes! Will Seiya be able to master thesenew techniques before the drawbacks wipe out his party?!