The multilayered mystery surrounding the Manten Aquarium and the disappearance of Mayu's sister, which slowly unveils through the game's branching narrative. Players experience a sense of uncertainty as they uncover clues and make choices that significantly impact the story's direction and outcome.

The exploration of psychological horror elements, such as the characters' personal struggles and trauma, which add depth and complexity to the narrative. For example, the game delves into Mayu's own experiences and motivations, leading to a compelling character arc as she navigates the aquarium's horrors.

The nonlinear storytelling with over 30 endings, the majority of which are 'bad' endings. This creates a strong incentive for players to replay the game, as they strive to uncover the full narrative and the various perspectives it offers.

The meaningful choices players make throughout the game, which significantly impact the story's direction and lead to the diverse array of endings. Each choice feels meaningful and consequential, shaping the player's experience.

The effective implementation of the 'New Game+' feature, which unlocks additional content and perspectives after completing one of the true endings. This encourages players to replay the game, as they can explore new narrative branches and deepen their understanding of the story.

The excellent soundtrack that enhances the game's unsettling and oppressive atmosphere. The range of musical styles, from introspective piano pieces to eerie, unsettling tracks, effectively sets the tone and heightens the sense of dread.

The sound design and audio cues that contribute to the overall immersive experience, further reinforcing the aquarium's unsettling ambiance.