Yogiri and Tomochika are finally reunited with their classmates as they make it to the capital of Manii. But before they have time to even say hello, they find the class already burdened with a new task: to accomplish a great feat that would gain them recognition as potential Sages. As the two try their best to blend in and smooth over the rough feelings from their previous abandonment on the bus, the class begins making plans to take on the Underworld, a labyrinthine dungeon below the capital, housing a Dark God they must slay to prove themselves worthy as Sage candidates. Meanwhile, another estranged classmate makes her return, but with far more sinister intentions.