Osamu and Youko Sonoyama want more than anything to adopt every child from Soramame House, but the wealthy couple can only pick one due to their increasingly old age. While they contemplate this delicate decision, one child's alluring beauty and gentle soul instantly draw them in. Two months later, the Sonoyamas welcome 13-year-old Hitori into their warm and loving home. However, Hitori's humble and overly polite exterior is merely a masquerade. In reality, Hitori is a carefully crafted character played by identical twins Migi and Dali. For them, being the ideal child of this kind couple is merely a stepping stone to infiltrating a certain quiet town. While dutifully protecting their cover, the twins work toward their true objective: to discover the truth behind a past incident that left them with a burning desire for vengeance.

Ron Kamonohashi, the best student in the history of the elite Detective Training Academy BLUE, has been living as a recluse since BLUE expelled him five years ago. Moreover, he is forbidden to work as a detective, having barely escaped execution after getting involved in a murder case while he was still attending the school. Ron's situation changes drastically when police detective Totomaru Isshiki, following the advice of a senior colleague, seeks him out for help with a criminal case that has remained unsolved for months. Ron reluctantly agrees to help Totomaru and uses his phenomenal intuition to discover the culprit in less than a day. However, it appears that Ron suffers from a mysterious condition that can cause those around him to lose their lives. To Ron's great surprise, Totomaru manages to save the life of someone whom Ron put in jeopardy. As the unlikely duo starts solving crimes one after another, BLUE sends operatives after its former student to find out if he has resumed investigative work. Fighting against murderers, rogue detectives, and the Metropolitan Police Department, Ron and Totomaru must join forces if they want to survive and see justice prevail.

Seina's epic misadventures are moving from the depths of space to his home on Earth. While he's made just as many friends as he did enemies on his journey, it's time to go back to those he loves on his own planet. But he quickly learns that things aren't the same as they used to be.

Kaoru Tono heard a rumor: The laws of space and time mean nothing to the Urashima Tunnel. If you find it, walk through and you'll find your heart's desire on the other side...in exchange for years of your own life. One night, Kaoru just so happens to find himself standing in front of a tunnel that looks suspiciously like the one the rumor describes. He finds himself thinking of Karen, the sister he lost in an accident five years ago. To Kaoru's surprise, he's been followed by the new transfer student Anzu Hanashiro, who promises to help him experiment with the mysterious tunnel—but what does she want from Kaoru in exchange? And what will he have left to give, after the tunnel's done with him?