In the distant future, in a distant corner of Siberia, people live in domed cities called Domepolises. These are the primary human living spaces on Earth, which became uninhabitable years ago from environmental destruction. Now, parts of the Earth are becoming habitable again. Large portions of the Domepolises are breaking off to escape the powers that control the domes and trade.

Gainer Sanga, video game champ on his 200th victory, becomes an unwilling helper in his hometown's Exodus when he is wrongfully arrested by the Siberian Railway. He pilots a giant mecha which he dubs 'King Gainer' after his own video game handle. He is challenged to fight other Overmen as Yapan tries to escape across Siberia.

(Source: AniDB)