Steins;Gate: Youen no Valhalla

遥遠のヴァルハラ

The Distant Valhalla is a side story set in the Alpha Attractor Field. It is set 1 year and a half after the Rounder Raid on the lab, and is about "Operation Valhalla", Okabe's plan to escape from SERN's captivity. (Source: wikia)