Bofuri: I Don't Want to Get Hurt, so I'll Max Out My Defense., Vol. 17 (light novel) — Yuumikan

ONWARD, TO THE TENTH STRATUM! Maple Tree is getting closer to the ultimate boss, the Demon Lord. After learning of an item known as the Demon Lord’s Mana, which will lead the guild to the notorious villain, they head for the tenth stratum—an amalgam of every zone that has come before. While the other members focus on separate areas, Sally and Maple visit the third-stratum section to upgrade their flying apparatuses. That’s not all they need to prepare for the fight, though. The girls tackle bundles of quests to increase their stats, and it’s finally time to boost Maple’s HP! However, in the back of their minds, they know the clock is ticking. The girls’ lives IRL are soon going to be busy again. Can they clear the stratum in time?