Masato Kadowaki (門脇 将人, Kadowaki Masato) is the major antagonist of the series. He is the former best friend and now bully of Arata Hinohara. He had a intense hatred toward Hinohara since middle school, therefore he plays the major antagonist in the series. After Hinohara helps him defenseless against Ameeno, it is uncertain that Kadowaki now regrets about Hinohara.
Kadowaki has brunette hair and hazel colored eyes. He wears the same uniform as Hinohara's although not as neatly. Kadowaki represents himself as a Yankee. His features are more sharper compared to Hinohara representing Kadowaki as more intense.
Later on in the series, Akachi rips Kadowaki's eye out of its socket with the tip of Akachi's Hayagami. Akachi almost immediately replaced it with Akachi's own "dead" eye. It is better than Kadowaki's original eye, as it lets him see "everything" more clearly.
Kadowaki is a complicated young man. He started off as a kind adolescent only interested in sports, where his favorite event was running track. However, his personality grows sour during middle school when his mother abandons him and his influential father begins adulterous affairs. All this chaos builds anger within Kadowaki and through his stubborn pride he refuses to accept the abandonment. He grows jealous of Hinohara who is well-liked for his personality and not through his family's financial affairs. Kadowaki begins bullying his best friend as a means to satisfy his own loneliness and bitterness. When both "Aratas" change roles he suspects something is amiss. Kadowaki's mental condition grows increasingly worse as he fights with his father and upperclassmen on a regular basis. Finally, he snaps and attacks an upperclassman. While running from the older boys, the Six Shou sense his hatred for Hinohara and drag him over to Amawakuni in place of Harunawa. In the anime/chapter 45, Kadowaki grows more malicious when presented with the dark Hayagami, Orochi, as his intent to defeat Hinohara is finally within reach.
After being presented with the dark Hayagami, Kadowaki begins to pick more battles with Hinohara and his one goal is to make the other teenager submit to him. His cruelty increases to the point of finding enjoyment in other Shou's pain as he forces them into submission. While hope seems lost for Kadowaki's humanity, there are hints of a gentler person hidden underneath the cruel exterior. Miyabi is the first person who gets Kadowaki to actually admit, though aggressively, about his and Hinohara's original friendship falling apart. And through his friendship with her does he begin to show concern for other human beings, this small sign of kindness is also extended to Harunawa's Zokushou, Munakata, who serves as a father figure towards the young man. While he is stubborn to admit his initial feelings with them, he slowly begins to break down his walls and starts to show small signs of sadness over his lost friendship with Hinohara and their current status as enemies.
His father is a wealthy businessman whose very influential in his business; unfortunately he begins to have affairs despite being married to Kadowaki's mother. Kadowaki began to turn into a cruel person as his father's actions caused the family to split. Much of Kadowaki's behavior is due to a lack of a positive father figure, his mother's abandonment added salt to an open wound. Kadowaki's kneel got permanently injured in a car accident which he might not run track-and-field like he used to, and Hinohara purposely loses in an important race tournament. Kadowaki believes Hinohara looks down on him, and constantly bullies him.
Orochi (逐力, Orochi) is Tsukuyo's counterpart.
- Arata Hinohara: Both boys were best friends until Kadowaki's personal life goes out of control causing him to lash out at his peers. Hinohara is more kindhearted than Kadowaki, which the latter uses to his advantage as making Hinohara a puppet for his own amusement. Kadowaki has some vulnerable moments where he reveals that he wishes to be better than Hinohara who was liked based on his own attributes instead of financial prestige.
- Miyabi: Harunawa's servant, but now Kadowaki's. Although Miyabi is not the brightest of characters, she is one of the few characters that keeps her skin intact after annoying Kadowaki. Although Kadowaki is self-interested, he begins to grow concern over Miyabi after she explains her family and health issues. Miyabi truly wishes to become Kadowaki's friend and listens to Kadowaki lament over past events. She offers advice which Kadowaki brushes aside, but it is obvious that he does listen to her ramblings. She may become a love interest in the future since it is shown that Kadowaki does show some concern for her well-being.
- Kadowaki's favorite food is fried food according to Yuu Watase's blog.
- Despite his initial antagonism towards Hinohara and claims on not being friends anymore, there are certain glimpses throughout the manga that show small signs of regret from Kadowaki's end for his bullying towards Hinohara.
- Out of all Shou and Zohushou that he forcefully absorb for power, Isora and Kanate are currently the only Shou who willingly submit to Kadowaki's Hayagami.