Each major sector of the underwater facility culminates in a boss fight against unique entities, including the titular "Sisters". These encounters operate as mechanical skill checks, requiring players to memorize attack patterns, execute well-timed dodges, and exploit brief windows of vulnerability to survive. Visual Art, Animation, and Audio
A major mechanic involves "confining assaults" where Hasumi can be rendered immobile by hazards like sticky fluids, parasites, and hypnotism. These status effects often persist even after a player clears a stage. Environment: mission mermaiden hasumi and the deep sea sist verified