Naibu Shizuka

"Lets all calm down here and take this slowly... When you work yourself into a lather, bad things happen. Take a few deep breathes and seek the calm. People generally lose their heads when they loose themselves to anger."

- Naibu's comments to Kentaro Hiroshi and friends.

Naibu Shizuka (内部静か, Shizuka Naibu, lit. Inner Calm) is a Shinigami who holds the rank of Master within The Ryu Order. A former member of the Gotei 13 who switched his allegiances because of his entire family being massacred by the order of the Central 46 on false rebellion claims. Taken in by Kusaka Kori and Sojiro Kori upon hearing about a fugitive Shinigami hiding in the Rukon District, Naibu became a member of the Ryu Order and immediately rose to the rank of Master through his unwavering desire to protect the weaker recruits. Charged by Kenji Hiroshi to protect the youngsters Kentaro Hiroshi, Harumi Kazuki, Jinta Kanō and Riki Nagakura as they make their way around the human world; he is one of the reasons why Kentaro and his friends have survived their encounters with the Imawashī so far and haven't been swept away and annihilated in the criminal worlds search for Shūhen Kōhai's legendary Bakkōtō.

Personality
Naibu's personality fits with his calm appearance, as he is a calm, but firm man, who believes that a calm disposition not only saves lives, but helps preserve the peace as those in leadership roles would be more open to diplomacy than open conflict. He and Kenji share a firm and unwavering friendship, rivalry and sense of brotherhood, as both were trained by Maki Zhijun in the ways of combat and strive to keep the ancient teachings of the Yuengiri alive. These similarities often lead to comical situations between the two in terms of leadership, though few among the Order trust one another to the degree Naibu and Kenji do; shown from Kenji's willingness to entrust the care of his son to Naibu.

Naibu, much like his mentor, takes a great deal of interest in the development of his students; most notably Jinta Kanō, the reason being given that Naibu "sees something of himself in the young man." An individual with a burning resolve and indomitable spirit, Naibu will fight for those he considers a friend until he drew his last breathe and has shown no hesitation in battling superior foes, stating "It's because I'm calm and composed that I'm able to fight you effectively", sharing similar personality traits in that regard to Uryū Ishida.

Kusaka Kori has stated that Naibu is a strange one, because of his likeness to Kenji Hiroshi being the sole reason for the statement. Like Kenji, Naibu values his freedom, shown from how he broke away from the Gotei 13 to join The Ryu Order upon the death of his family; an event he harbors great hatred and anger towards. His sense of freedom, however, pales in comparison to Kenji's, as Naibu retains a polite and respectful tone when addressing others, even if hes angry.