Arimaru is a member of the Muhou School and one of the members of the leaders Personal Corps. She is also known as the ant.
Arimaru is a large, brutish woman with dark skin. Despite her gender she's a huge, muscular body, to the point that she's larger than most of the male characters. She has long light colored hair that extends past her shoulders. Her face is overall flat and very much lined, though she sports unusually thin lips. She wears a light colored sleeveless overshirt over a black under shirt with light colored shorts and a black belt. Her toes are longer than average, and her nails resembles claws. Due to her looks, many characters refers to her as a "monster", or even a "demon-possessed person".
Arimaru is a calm person. When she is given work, she will face them depending on who the opponent is. She seems excited to face the Ogame School. When someone wounds her, she will become enraged. She seems to prefer solitude (possibly because of her grotesque looks) and seems to kill subordinates and even women and boys to pass the time. She also tends to call other people (namely Shimon and Shinnojo) "cute".
At some point, Arimaru had joined the Muhou School and became a member of the Personal Corps.
Arimaru first appeared in a cell underneath a castle wall, cowering in her room with dead subordinates lying around. Shimon comes and tells her that he has some work for her. Shimon tells her to take out the Ogame school, which she seem excited about.
When the Ogame school and their allies enter her territory, Arimaru attacks them from below. She is able to wound Gensai, Kashitarou, and Arata. Arimaru then sticks her head out of the sand and tells them to come and get her when Shinnojou says that he will kill her. Shinnojou wounds her by stabbing her through the sand. She becomes extremely angry and then gets out of the sand, ready to face Shinnojou. She picks up her giant shield from the sand and brace herself for the battle by running at Shin, trying to slam him. She is able to harm Shinnojou and tries to finish him off but Zenmaru stops her, diverting her attention on himself.
Arimaru rushes at Zenmaru , overpowering him with her shield and is disappointed when she finds out that the boy is weaker then she thought. She repeats the shield bash attack one more time, injuring the young Ichinose, but as she moves in for the kill Zenmaru finally realize the real potential of his sword and manage to repeal her. Outraged and surprised, Arimaru pretends to lunge at Zenmaru, only to pull a sneak attack taking advantage of the shield' size. However her plan is foiled by Zenmaru, who breaks her sword much to her shock. Panicking, she decides to run back to the hidden entrance in the ground to repeat her underground tactic, but before she can reach the hole Zenmaru attacks her with Shuengetsu, the final technique of the Kagutsuchi Kata, mortally wounding her. As she falls down she wonders how she could lose to someone like him.
Thanks to her body, Arimaru is gifted with an herculean strength, allowing her to move her giant shield with ease and even run with it. She fights at her best inside her special sand-filled arena, attacking from an underground tunnel. Thanks to her keen perception she can pinpoint with great accuracy the position of her enemies as they move on the sand. She can also move very well on the sandy ground, a fact that she takes advantage of when fighting outside of her tunnel. She's also proficient with many weapons.
Arimaru's Spike: Arimaru is first seen using cone-shaped spikes with a spiral motif to impale her victim's feet from underground.
Arimaru's Sword: a gauntlet-sword resembling an indian Pata worn on her right hand.
Arimaru's Shield: When forced to come out, she picks up a huge metal shield, big enough to cover her whole body, with a small slit in it where she can put her sword in.
Sunakari no Jin (Sandy Hunter's Formation): Arimaru puts the sword through the shield then rushes forward. If the opponent is not impaled then they are sent flying after being hit.
- According to the author, Naosuke Nakamaru, Arimaru started as a male character, but eventually he was persuaded by his editor to turn him into a female, leaving her appearence unalterated, even though other characters also refer to her as "male".
- During the Eastern Gate Arc, during the reunion of the Special Corps where she and Toujou where missing they were referred to as number 3 and number 10. However is unspecified who's who.