Ōgon Musōkyoku (黄金夢想曲), licensed in English as Umineko: Golden Fantasia, is a 2D versus fighting game developed and published by 07th Expansion. It is considered a spin-off of Umineko no Naku Koro ni and was originally released at Comiket 79 on December 31, 2010. The game was later ported to the Xbox 360 by Alchemist on October 6, 2011 under the title Ōgon Musōkyoku X. An append disc to the original game titled Ōgon Musōkyoku Cross was released at Comiket 81 on December 31, 2011. The game was adapted into a manga illustrated by Morozumi Junka and serialized in Kadokawa Shoten's Comp Ace magazine in December 2011.
Ōgon Musōkyoku is a fighting game that can be played by up to two players. Gameplay revolves around a tag-team battle system in which each player takes control of two characters, only one of which can be controlled at a time, but both of which can be switched out with the other through the game's "Touch" system. A "touch" can only be performed when a player's Touch Gauge is full (the gauge fills on its own over a set period of time). There are five kinds of touching methods, each of which uses up a different amount of the Touch Gauge: Normal Touch, which is used when the player isn't performing any other action; Attack Touch, which is performed when the player is in the middle of attacking an opponent; Guard Touch, for when the player is guarding against an opponent; Damage Touch, which can only be used when the player is damaged, and has the additional effect of creating a barrier that forces the opponent away from the player; and Assault Touch, in which the player performs a rushing attack towards an opponent before switching out.
Every character in the game has a unique ability which can be used to improve their own skills or their partners' skills for a limited period of time. There are two methods of activating abilities. The first method is through touching, which automatically activates the ability of the character being switched out and affects the character being switched in. The other method is by summoning the Metaworld, which not only drastically changes the background, but also activates the abilities of both the player character and his or her partner at the same time. The Metaworld can be summoned through use of the SP Gauge, which also allows characters to perform special, powerful attacks called "SP Supers" and "Meta Supers". However, two players cannot summon the Metaworld at the same time; the first player to summon the Metaworld will benefit from its effects, but it is possible for the other player to cancel out the opponent's Metaworld. The Metaworld will remain active until the summoner's Meta Gauge runs out.
The game is set on the island of Rokkenjima, where a series of mysterious deaths and disappearances take place over the course of October 4 and 5, 1986. The story focuses on a game of twisted logic between Beatrice, a legendary witch who claims she used magic to perform the murders, and Battler Ushiromiya, a young man who argues that the murders could be carried out by ordinary humans. As a tag-team game, the game's story mode follows multiple pairs of characters, each of which has their own story and ending that take place in an alternate continuity from Umineko no Naku Koro ni.
- Data-mined audio files indicate that it may have been originally possible for players to choose the same character as both Attacker and Reserve, but this feature was scrapped.