Kyousogiga

Also known as:  Kyousougiga, Kyosogiga

The web anime Kyousogiga is created by studio Toei Animation and co-produced by toy maker Banpresto. In this absurd sci-fi action story, three kids are stuck in a strange city causing massive mayhem through the land. They are searching for an atypical rabbit in order to return home. Koto, the eldest of the three, seems to have some sort of connection to this weird place ruled by a monk, a demon, and a priest. (based on ANN synopsis)

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Producers, official website and other details: AniDB, ANN, Wiki