Akihabara Dungeon Bouken Kitan

Akihabara Dungeon Bouken Kitan (秋葉原ダンジョン冒険奇譚) is a light novel series by Kumin Nakano with illustrations by Rein Kuwashima.

Plot
The Akihabara Dungeon—it's a new dungeon that has suddenly appeared at the remains of what was once the Radio Kaikan building.

The interior of a dungeon is a mystical area where mana exists and mechanical technologies become useless. Within such place, the notion of danger exists every corner along with the endless monsters; dungeons can be remarked as the epitome of a "fantasy world." It is where "adventurers" who thirst for discovery and excitement live a life consisted of daily explorations...

Shouma and Rio are high school students that spent their summer vacation exploring the dungeon in Akihabara. Due to some circumstances, they met each other and have set out to become legendary explorers. With Akihabara as the setting, a new epic that ties daily life with fantasy has begun its prelude.