The character known as Kemeko is the titular robotic suit from the series. Its true nature is that of a powerful combat robot, distinguished by a small, chubby, and somewhat doll-like physique that belies its immense strength and agility. The robot is piloted from within by a tall, attractive, pink-haired girl who goes by the alias M.M., though her real name is later revealed to be Mei Mishima. Because the pilot rarely exits the suit, most characters in the story are unaware that Kemeko is a machine and believe it to be her true form.

Kemeko’s personality is a direct reflection of its pilot’s state of mind. When inside the suit, Mei Mishima adopts a strong, assertive, and sometimes aggressive demeanor, claiming the role of protagonist Sanpeita Kobayashi’s bride and acting as his self-appointed protector. However, when she exits Kemeko, her true personality is revealed to be much more timid, shy, and prone to hesitation, suggesting that the suit gives her a sense of confidence and purpose she otherwise lacks.

The motivation behind Kemeko’s actions is rooted in a complex past. Ten years prior to the main story, a girl who was Sanpeita’s childhood friend fed him a mysterious seed known as the Nano Ball, which possesses limitless energy. This event led to a catastrophe that resulted in the girl, Mei, having all her memories of Sanpeita erased and her father being mortally wounded. Before dying, her father gave her the Kemeko suit and sent her away, tasking her with protecting Sanpeita and the powerful Nano Ball now hidden within his body. Living with Sanpeita as his guardian serves as a constant, painful reminder of the memories she has lost, which she desperately wishes she could recall and keeps a journal of.

In the story, Kemeko functions as Sanpeita’s guardian and self-proclaimed fiancée, intruding into every aspect of his life to protect him from the relentless attacks of the Mishima Corporation, which seeks to recover the Nano Ball. To remain close to him, the pilot uses the Kemeko guise to move into his home and even secure a position as a teacher at his school. Her key relationship is, of course, with Sanpeita Kobayashi, the young man she is sworn to protect and towards whom she develops genuine romantic feelings. She also has a significant rivalry with Izumi Makihara, Sanpeita’s childhood friend who also harbors feelings for him. A central relationship is with her twin sister, Mai Mishima, who is the primary antagonist and the one responsible for the original incident that led to Mei’s memory loss and the implantation of the Nano Ball in Sanpeita.

Throughout the series, Kemeko, as an extension of Mei, shows notable development. Initially, the pilot is almost always inside the robot, hiding her true self. As Sanpeita encourages her to be herself, she begins to emerge from the suit more often, especially out of jealousy to compete for his affection. By the conclusion of the story, she overcomes the tragedy of her lost past, falls in love with Sanpeita all over again, and truly becomes his fiancée, choosing to seal the power of the Nano Ball for good. As a combat unit, Kemeko possesses formidable abilities, including high-speed flight, significant destructive power, and the agility to easily defeat other robots, making it a highly effective piece of defensive and offensive technology.