When the story begins without its hero Kimihiko Kimizuka has always been a magnet for trouble and intrigue. For as long as he can remember, he’s been stumbling across murder scenes or receiving mysterious attache cases to transport. When he met Siesta, a brilliant detective fighting a secret war against an organization of pseudohumans, he couldn’t resist the call to become her assistant and join her on an epic journey across the world. …Until a year ago, that is. Now he’s returned to a lif...

WHO WERE YOU TO HER? WHO WAS SHE TO YOU? While on an outing one day, Kimihiko Kimizuka and his three friends are kidnapped by…Siesta herself?! But they soon learn there’s more to the story as she reveals the long-forgotten truth about Siesta’s death. Will this be the clue that finally unlocks the secrets of Kimihiko's past?

After saving the world from collapsing, the two Ace Detectives and their assistant, Kimihiko Kimizuka, are immediately thrust into the next crisis: the Tuner Hunt. But when the likely culprit surfaces, it turns out to be the most unforgettable girl of all! Meanwhile, a client visits the Shirogane Detective Agency claiming to have been reunited with Kimihiko’s teacher—a man who supposedly died eight years ago. What is real and what is fake? What’s true and what’s a lie? Within four locked r...

The proxy detective is living her dream.All Nagisa Natsunagi wanted was to be a regular high schooler, and right now, that’s all she is. The most special thing about her is that she was too sick to come to school for a long time—but that’s all in the past now thanks to a successful heart transplant. At long last, she’s finally living the life she always wished for! Still, she can’t help wondering about her donor, and there’s a boy in town who can solve any case. Maybe he can help?

Reunited with Siesta, Kimihiko is pulled back into action as assistant to the Ace Detective. Together, the two face off against Seed again and, with a little extra help, defeat him. Although that particular crisis may be over, the journey to awaken Natsunagi continues. In search of clues for how to save her, Siesta and Kimihiko travel to New York City. However, instead of answers, they find trouble brewing with the Phantom Thief—and worst of all, Siesta disappears!

What’s wrong with this story?After being kidnapped, Kimizuka, Natsunagi, Saikawa, and Charlie have learned the truth about Siesta’s death...or have they? A girl who looks just like the deceased appears and informs them that the footage they’ve been investigating contains an error. As they hunt for an answer to a mystery that even Siesta couldn’t uncover, the group will learn what it truly means to inherit the legacy of an ace detective. Though the detective may already be dead and the trut...

“Let me tell you the story of a man who lived and fought through each and every day.”With the world in peril once again, Kimihiko Kimizuka returns to his role as the Ace Detective’s assistant and sets out on a journey to recover the lost memories of humanity. Using the Sacred Relic discovered by the Oracle, he investigates a past global crisis with the Vampire, Scarlet, at the very heart of it. But as Kimihiko delves deeper, harrowing truths once beyond his reach begin to bubble to the sur...

Once the assistant to a great detective, Kimihiko Kimizuka took on a challenge Siesta bequeathed to him after her death and arrived at a conclusion that surpassed his wildest expectations. To bring back the great detective—the stuff of miracles—Kimihiko and Natsunagi fly to London yet again to obtain evidence that can bring down Seed. On the flight there, however, he hears the same words as he did four years ago: “Is there a detective on the plane?”

“Let’s go on a journey to unlock the world’s secrets.”Kimihiko Kimizuka was once the assistant to two Ace Detectives, and after achieving a miracle, the sequel to the story was ordinary life. The Ritual of Sacred Return was supposed to be the moment world peace was achieved—but instead, it was discovered that something was wrong with the memories of the world. As the search for the truth begins, it seems Kimihiko’s memories of his brief but extraordinary adventure with another Tuner, Rill,...

Everyday life is a precious gift.Nagisa Natsunagi was enjoying her daily routine with her two best friends, finally living out her dream of being a normal high school girl—at least, until she found the detective she was looking for. The summer afterward was full of adventures and new encounters, but now that she’s back at school with her friends, will she be able to find that normal life again?

The second act is about to begin.The adventure of the detective and her assistant began ten thousand meters above the earth. They helped clients, solved cases, fought powerful enemies, and traveled all over the world—and then the detective died. The story should have ended there. But a year later, one girl’s passion set it in motion again. After many battles and sacrifices, a miracle was granted. Now that it’s all over, Kimihiko Kimizuka is basking in the ordinary life that comes afterward...

Siesta and Kimihiko’s first meeting did not take place during that fateful plane hijacking but rather four years earlier, when the Federation Government tasked Siesta with locating a spy in Japan. During her undercover investigation, she happened upon her future assistant, who had a connection with the spy she was looking for. With Kimihiko as her only lead, she enlisted his help in the search. But Siesta hid her identity with constant disguises, so unbeknownst to Kimihiko, he had already ...