Cladun: This is an RPG, known in Japan as Classic Dungeon: Fuyoku no Masōjin (クラシックダンジョン 〜扶翼の魔装陣〜, Kurasshiku Danjon ~Fuyoku no Masōjin~, lit. "Classic Dungeon: Assistance of the Devil Formation"), is a 2010 action role-playing video game developed by System Prisma and published by Nippon Ichi Software (its parent company) for the PlayStation Portable. The game was released in Japan on February 18, 2010, in North America on September 20, 2010 and in Europe on November 17, 2010.

Cladun: This is an RPG features cooperative and competitive gameplay with up to three other players.^[1][2] Dungeons are randomly generated and the game features customization of not only the main character but also the final boss. Developer Souhei Niikawa compares the game's retro art style to What Did I Do to Deserve This, My Lord?, another Nippon Ichi title.^[2] Two sequels for this game were released, ClaDun x2, which was released in 2011 for the PlayStation Portable, and was made available for PC via Steam on August 14, 2012, and ClaDun Returns: This Is Sengoku!, which was released for the PlayStation Vita, PlayStation 4 and Steam in 2016-2017.

This article needs an improved plot summary. (September 2013)

The story starts with a girl named Pudding and a boy named Soma going to a gate that Pudding believes is a way to go to the magical world "Arcanus Cella". Upon entering, they find themselves in Arcanus Cella. The story progresses as the player finishes levels to unlock characters and places. Each time a floor of a dungeon is finished, more floors are unlocked and sometimes a scene may unlock new characters, or show something about the characters in the game.