Naka-Oni

The Naka-Oni (中鬼, Naka Oni) is a fictional character in the manga series of Shaman King. It is a Oni that can be summoned by Kyōyama Anna and her son Asakura Hana.

About
The first Naka-Onis seen was unwittingly created by Kyōyama Anna's uncontrollable Reishi (霊視) power. The second one seen was summoned by Asakura Hanna due to a power given to him Asakura Hao were he, in a state of near death, goes into a trance and summons various sizes of Onis to defend himself. Unlike his mother who summoned one without realizing it, Hana actively summons the larger Oni by chanting "Demons Out".

Osorezan Revoir
It was created when Kyōyama Anna and Asakura Yoh went to a temple on new years day. When the prayers, hopes and worries exceeded 1080, something that easily happened during that time and place, Anna's Reishi powers went out of control and created the Naka-Oni.

While fighting with Matamune when Anna's powers went way out of control, it began gathering the surrounding Oni in the area. The Oni began devouring each other and in the end, the Naka-Oni would evolve into Oh-Oni.

Flowers
When Ichihara Ryuji almost killed Asakura Hana by fracturing his skull he went into a trance and began summoning Oni at random to attack Ryuji and Asakura Luca. As Luca destroyed all the Onis he summoned, Hana began chanting and summoned bigger Onis even a single Naka-Oni though it to was destroyed by Luca's Over Soul. In response Hana gathered the regenerating remains of his Onis to create a Dark-Oni that was finally able to defeat Luca.

Anime/Manga Difference
Naka-Oni is a manga only character and never appears in the anime.