The homeroom class gets sucked through a wormhole into - you guessed it! - another world where they encounter a desolate environment dominated by a rampaging magical automaton. There they meet a girl-type golem with mannerisms similar to Megumin, a woman dressed in the same military uniform as Tanya, and a man with a cane who seems to know Subaru, and hijinks ensue.
(Source: Crunchyroll)
