Short answers, pulled from the story.
Super Gem Fighter Mini Mix is a 1997 fighting game developed and published by Capcom for arcades. It uses super deformed character designs shared with Super Puzzle Fighter II Turbo and was ported to PlayStation, Sega Saturn, and WonderSwan in 1998.
Playable characters include Ryu, Ken, Zangief, Chun-Li, Ibuki, and Sakura from Street Fighter; Morrigan, Hsien-Ko, and Felicia from Darkstalkers; Tessa from Red Earth; and secret characters Dan and Akuma. Ibuki is the only Street Fighter III character in the playable roster.
When a player lands a hit, gems burst out of the opponent and can be collected to level up special moves across three color-coded Gem gauges. Players can also collect elemental orbs to throw at opponents, potentially freezing them or turning them to stone.
Costume Combos, also called Flash Combos, are four-hit sequences that cause characters to transform into different outfits mid-combo, inspired by the Plasma Combo system from Star Gladiator. For example, Chun-Li may become her version of Jill from Resident Evil, while Felicia may transform into her version of Mega Man.
Next Generation rated the PlayStation version three stars out of five, PS Extreme gave it 80%, and PSM Magazine scored it 3.1 out of 5. In Japan, Game Machine listed the arcade version as the ninth most successful arcade game of November 1997.
The game was ported to PlayStation, Sega Saturn, and WonderSwan in 1998. It was included in Street Fighter Alpha Anthology on PlayStation 2 in 2006, and appeared in the Capcom Fighting Collection released on Nintendo Switch, PlayStation 4, Windows, and Xbox One in 2022.