Nobody remembers this thing exists, which is exactly why it works. A kid wakes up with no memory of saving two worlds, a girl builds a mecha out of Tokyo garbage, and somehow the OVA treats all of it like the most natural continuation ever. The whole thing moves so fast and commits so hard to its own absurdity that you stop asking why and just ride the chaos.

Lamune is back on Earth and remembers nothing of his earlier adventures in Hara-Hara world and Doki-Doki space. What is left of Gobuhriki has reached Earth, and it rouses the spirit of Don Harumage. In Tokyo, Cocoa assembles a combat vehicle out of odds and ends she gathers around the city. Meanwhile, Milk and Leska go looking for Lamune and Da Cider, hoping to save the day before a new Gobuhriki comes back to life and wipes out the planet. The result is a three-episode comedic fantasy adventure with mecha action, set after the Lamune & 40 TV series.