Yumi Kikuchi

A serial-murderer is on the loose who just so happens to also be removing the hearts of his victims and taking them with him. His victims however, are not merely random humans as thought by the police. They are in fact, the past and present guardians of the gateway of the afterlife.On the day he is to be married, Detective Kanzaki, who happens to be on the case, discovers that his fiancé Mina has been murdered with her heart also missing. He also learns that the killers are Kudo, a geneticist, and his evil secretary Rei. The two are trying to obtain six hearts from the guardians so that they may call forth a horde of demons from the Gate of Rage and have their every desire granted. Only problem is, once they open the gate the entire world will be covered in darkness.

In the last chapter of the Refrain Blue series, the bond between Yoshihiro Matsunaga and Nao Morisawa grows stronger, while Yoshihiro finally finds out the identify of the mysterious girl from the first chapter.

The second chapter in the Refrain Blue series focuses on Nao Morisawa and the events that happened at the summer camp last year, with her and Yoshihiro Matsunaga both unable to let go of feelings of the past.