Seiji Kameyama

, also known as, is a third-year at Ishiyama High School. He is the bassist of the Poltergeists.

Appearance
Kameyama is a tall, lean-built young man with dark hair and dark eyes.

His hair reaches just down his neck and is mostly slicked back, save for a long wavy lock that falls over his nose, which sometimes sways towards the left side of his face while he walks. He also has thick sideburns. Kameyama's face is notably scarred, as he has two below his weary eyes that are visibly crooked, as well as a much longer scar that runs through his mouth in an unorganized manner. He also has a round stud-like piercing on his bottom lip and two similar, albeit darker, earrings on both of his ears.

Kameyama wears a light-colored, closed shirt with an upturned collar that is patterned with dark circlets overlapping one another. Moreover, around his neck is a dark necktie that is considerably long. Over this, he wears a dark leather jacket that is left open but also has an upturned collar. Patterned on the back is a one-armed anthropomorphic turtle holding up a rabbit with the words "rabbit and turtle" written above the two animals. Below the waist, Kameyama wears dark pants and dark shoes. Around his left side is a metallic chain attached to a dark leather compartment, which is visually similar to a guard used to wrap around knives for quick use.

Personality
Kameyama is a uninterested individual who often maintains a calm and laid-back composure. He is relaxed even during heated situations such as a fight; during Hajime Kanzaki's attack on the Poltergeists, despite him having easily beaten Shioiri after taking a beating, Kameyama reassures them both that Shioiri had been caught by surprise. Kameyama's words show that he also has a certain level of confidence over the power of his fellow Poltergeists.

History
Before enrolling in Ishiyama High School, like the rest of the Poltergeists, he attended Sōrei High School.

Return to Ishiyama High School Arc
On the first day of the semester, all of the Poltergeists have planned to meet for band practice, though Nasu evidently fails to show up. Consequently, all of the other Poltergeists, including Kameyama, go out to get him; they see that he is out in one of the building's hallways and go to meet with him. Kameyama reminds Nasu that they are supposed to finish playing "Hare Hare Yukai". When Nasu realizes that it is time to go, he joins his fellow Poltergeists, and they all leave together.

The following day, while having some free time, Kameyama goes to the cafeteria where he buys juice from one of the vending machines; upon receiving his snack, he tries putting in the straw. It turns out, however, that this is actually a doppelgänger.

The real Kameyama is actually in a room with all of the other Poltergeists, where they later greet an intruding Hajime Kanzaki and Takayuki Furuichi. Kameyama darkly smiles at them and later laughs at Kanzaki's surprise on how crowded the room is. Kameyama then stands aside while Kanzaki is being beaten up by Shioiri and Teruomi. As he looks on at the defeated Tōhōshinki, an unusual tattoo appears over Kameyama's collarbone, with the number 2 directly above it.

However, Kanzaki manages to rise up and surprisingly defeat Shioiri with a single punch; such an unexpected comeback surprises Kameyama. The Tōhōshinki then turns to fight the rest of the Poltergeists alone. Kameyama assures Kanzaki that he only caught Shioiri by surprise and flings several of his bass picks at Kanzaki, each of them piercing through his skin. He then looks on as his fellow Poltergeists deal their own attacks at Kanzaki and seemingly defeat him; unfortunately, he manages to make another counterattack by kicking and consequently knocking Teruomi unconscious, which puts Kameyama and Onizuka both at unease. Unfortunately, Kameyama is later defeated and knocked unconscious due to Kanzaki.

Equipment
Bass Picks: Kameyama is a bassist, and as expected of him, he possesses bass picks, having at least four that he carries on hand. His bass picks are triangle-shaped and are generally dark, except for a light-colored border that edges around each individual bass pick. On one side, it says the word "BOY" plus additional written lines printed in small text below.
 * Flinging: Kameyama uses his bass picks as a form of attack, throwing them all simultaneously, which, when thrown at a certain strength, can easily puncture a grown man's flesh and cause blood to spew.