Spoiler scope: Contains spoilers for Season 1. No events from later anime seasons or unadapted source material are included.
Kimihiko Kimizuka tries to return to ordinary school life after losing Siesta, the detective he accompanied around the world. A new client, Nagisa Natsunagi, brings him back to cases that are inseparable from their shared past.
Siesta and Kimizuka: three years as partners
Their partnership begins during an airplane hijacking. Siesta appoints Kimizuka as her assistant, and together they confront SPES, an organization that creates superhuman agents through biological experiments. Three years of travel and investigations make them close companions, until Siesta dies.
A year later, Nagisa asks Kimizuka to identify the person behind the feelings left by her transplanted heart. Her donor was Siesta. Kimizuka becomes involved with Nagisa and the idol Yui Saikawa, whose artificial sapphire eye also attracts SPES.
Alicia, Hel and the heart that connects them
Flashbacks reveal how Kimizuka and Siesta took in Alicia, a girl with missing memories. Alicia and the dangerous SPES agent Hel share a body. Hel takes Siesta’s heart, but Siesta’s consciousness survives within it and suppresses Hel.
This is the link between Siesta’s death and Nagisa’s present identity. The heart carries more than memories, and Kimizuka’s new partner is connected to the enemy from his earlier adventures.
The Season 1 ending: Siesta’s legacy
On a cruise ship, Kimizuka and his companions are attacked by the SPES agent Chameleon. Nagisa lets Siesta’s consciousness take control of her body, allowing the detective and her assistant to fight together again. With help from Yui and Charlotte, they overcome the attack.
Afterward, Nagisa is herself again. She chooses to take up the detective’s role with Kimizuka beside her. Siesta’s loss still matters to him, but he can finally move forward with the people she brought into his life.
The quick reminder
- Nagisa has Siesta’s heart; Siesta’s consciousness can act through it.
- Alicia and Hel share a body and are central to Siesta’s death.
- Nagisa takes up detective work, with Kimizuka as her assistant.