"Futakoi Alternative" is a 13-episode anime series that blends elements of romance, comedy, and supernatural intrigue. The story centers around Rentarou Futaba, a young man who returns to his hometown after the death of his father, a private investigator. Rentarou takes over his father’s detective agency, which operates out of a modest office above a bathhouse. The bathhouse is run by the Mizushiro sisters, identical twins Nozomu and Shizuru, who are deeply connected to Rentarou’s past. The twins share a mysterious bond, often experiencing each other’s emotions and sensations, which adds a layer of supernatural complexity to their relationship.

As Rentarou settles into his new role, he becomes entangled in a series of bizarre and often dangerous cases, many of which involve supernatural phenomena or unresolved personal histories. The cases frequently draw Rentarou and the Mizushiro sisters into confrontations with eccentric characters, including a rival detective agency, a reclusive artist, and a group of enigmatic individuals with ties to the twins’ past. These investigations gradually reveal deeper layers of the twins’ connection, as well as Rentarou’s own unresolved feelings about his father and his childhood.

The narrative is structured around episodic cases, each contributing to the overarching mystery of the Mizushiro sisters’ origins and the strange occurrences in the town. The twins’ bond is a central theme, explored through their interactions with Rentarou and their shared experiences. Nozomu is more outgoing and assertive, while Shizuru is reserved and introspective, creating a dynamic that balances humor and emotional depth. Rentarou’s role as a detective serves as a vehicle to explore these relationships, as well as the broader mysteries of the town.

The series maintains a balance between lighthearted moments and darker, more introspective themes, with the tone shifting depending on the nature of the case. The supernatural elements are woven into the narrative in a way that feels organic, often serving as metaphors for the characters’ emotional struggles. The interplay between the episodic mysteries and the overarching plot ensures that the story remains engaging, with each episode contributing to the gradual unraveling of the central mysteries.

"Futakoi Alternative" is characterized by its focus on character development and its exploration of themes such as identity, connection, and the impact of the past on the present. The relationships between Rentarou and the Mizushiro sisters, as well as the supporting cast, are central to the narrative, driving both the episodic cases and the overarching plot. The series concludes with a resolution that ties together the various threads of the story, providing closure to the characters’ journeys while leaving room for interpretation regarding their future.