Little Complications (Little Tokyo #3)

Nate, a community college math teacher, enjoys a modest life until strange changes overtake his campus. His assistant Rachel transforms, departments adopt odd themes, and students begin failing while behaving like uniformed high schoolers. Investigating, Nate goes undercover in the only successful class, taught by a new Japanese instructor—disguised as a teenage girl.

He soon realizes his the school is transforming into a surreal Tokyo-like district, and he’s being absorbed into it. As reality warps, coworkers assume bizarre roles and identities, and Nate finds himself trapped in an increasingly strange world where his former life and authority are slipping away, and his life is becoming that of a schoolgirl in a world he doesn't recognize.

This is part 3 of 3, and the conclusion to the story "Little Tokyo."