Son of the leader of the Shimizu clan, Raiko was fifteen when he started to question his mother's rule. Raiko was not able to save a friend of his due to not being allowed to interfere with outside world affairs. His mother had told him to not help his friend, therefore leading to her ulitmate death. Soon, Raiko discovered that his uncle had similar thoughts as he, that they should be able to use their skills in the outside world. Thus leading to a mutany against his mother, led by his uncle who wanted to step in and take her role as head of the clan. One night, his uncle confronted his mother, telling her step down. Others, allong with Raiko were present. Raiko had been told by his uncle that there would be no blood shed, but when hs mother refussed to forfit her leadership, Raiko's uncle killed her and his father in anger. The clan had turned on each other, killing one another in the process. Taking up his white gamon (partner to Raimei's black) Raiko punished his uncle by murdering him for his crimes. The building caught fire and as Raiko stood over his uncle's body, and the bodies of his family, a 10-year-old Raimei walked into the horrifying sight. Knowing
how much his sister loved their uncle, Raiko took full blame for the murder of their family. He did not want Raimei to bear the burden of knowing what had become of them, so that she could remember them as good people. As he left, covered in blood, Raiko told his little sister that he was going to join the Kairoshu (Grey Wolves) now. Leaving her completely alone and thinking that her brother had just murdered their entire family in cold blood. Raimei soon grew a strong hatred for him, and five years later still works to hunt him down.
Now a punisher, he cuts down those who betrayed the Kairoshu, which led to his first meeting with Gau. A boy who had nearly died trying to avenge his parents death. The same person who had killed his parents had betrayed the Kairoshu. To Raiko, Gau was the friend he could not save those years ago, so he took him into the Nabari world and he became his partner.
Knowing his sister is intent on finding him, Raiko leaves spider lilies upon his victums so that he may confront Raumei at the place they grow near where was once the home of the Shimizu family. Raimei, not knowing of what truely happened that night, had taken it upon herself as a Shimizu to past judgement on her brother. The two battle, Raimei tells him that he has soiled the Shimizu family name. Their fight leads to Raiko cutting a deep wound into Raimei. He takes her sword, Kurogamon, and leaves her bleeding in the rain.
Later, Raiko finds himself confiding in his only real friend, Gau, who asked him about his past. He reveals to him the truth of what had really happened to his family. Raiko then makes Gau swear to secrecy of this and tells him if he reveals this to anyone else, there will be punishment.
But Gau is deeply moved by the story and believes that Raiko and Raimei should not be fighting, should not be enemies, but brother and sister. Without Raiko's knowing, Gau goes to the hospital where Raimei is. He tells her of what Raiko told him had really happened five years ago. Raimei is not fully convinced, but Gau takes a kunai and holds it to his throat. Willing to bet his life that it is true.
Once out of the hospital, Raimei returns to the spider lily patch within the forest for a rematch with her
brother. Raiko returns her sword but during their second battle disarms her anyways. Raimei breaks down crying, saying that Raiko should not have taken on the burden alone, that he should not have thought her so weak and uncapable of handling the truth. She ask him to come home but Raiko says that it is too late for that. Seeing characteristics of their mother in Raimei, Raiko forces her to take up Kurogamon and fight him once more. Raiko slashes down his sword for Raimei but finds that his blade had not hit Raimei but instead Gau who had stepped in. Gau tells Raiko, "I have come to accept my punishment." Gau falls, bleeding. He begs for the two to stop fighting and to just be brother and sister again. He apologizes for breaking his promise to Raiko to not tell Reimei and soon slips into comatose.
This distresses Raiko and causes a deep concern that Gau may not wake because he no longer wishes to see Raiko. Using his Kira, Yoite is able to awakens Gau. Feeling indebted to Yoite, Raiko defys Hattori, the Kairoshu leader, to help Yoite. Discovering that Hattori's true intentions for the Shinra Banshou are to erase everyone's memories, Raiko completely forfits his loyalty to the Kairoshu.
Portrayed as an easy-going, well-mannered person, Raiko Shimizu takes his responsibilities very seriously and is implied to be a sadist.
Hair: Salmon Pink (originally blonde)