What Rabi-Ribi is
Rabi-Ribi is a 2D side-scrolling exploration platformer in the Metroidvania mold, set on Rabi-Ribi Island. You play as Erina, a regular rabbit who ends up in an unknown world turned into a human with rabbit ears, and who wants her old life back. Along the way she picks up Ribbon, a cheerful pink-haired fairy who stays by her side. Erina handles close-quarters combat with the Piko Hammer, while Ribbon is the ranged attacker who follows Erina's lead and is controlled indirectly by the player, firing off spells from a distance. Battles are dense: you are dodging bullets, missiles and lasers while working out the patterns.
How a group plays it together
The Steam features list Remote Play Together, so one person who owns the game can bring others in to play along. Beyond that, the game itself is built around a single protagonist and her fairy companion, with the second character handled by the player rather than a second person. Boss Rush Mode is the natural pick for a group session: it lets you fight some or all of the 40+ bosses in a row, which makes for a good spectator-friendly run when people are watching each other take on the 1000+ attack patterns.
Before you start
The world is non-linear. Hints point you along a route, but nothing forces you to follow them, so wandering off the beaten path is the intended way to play. There are 9+ main areas and 20+ sub-areas, plus over 60 items and upgrades to collect, and which trinkets and skills you grab is entirely your call. Difficulty comes in 4+ settings, and the game explicitly invites you to try hard mode with no items equipped if you want the punishment. Expect a long haul: there is post-game story content, a speedrun mode that strips out every section where you cannot control Erina, over 50 pieces of original soundtrack, and support for English, Chinese and Japanese.