Teeth is one of three identical triplets collectively called the Mouth, alongside Lips and Tongue. Originating from the United States, the trio functions as a singular unit with seamless coordination in movement and speech, frequently finishing each other's sentences. Their physical appearances are indistinguishable except for their distinct voices.

Recruited by a prison warden, the Mouth was tasked with incapacitating the formidable former heavyweight boxer Iron Michael. Leveraging exceptional teamwork and combined martial arts skills, they overwhelmed him through simultaneous strikes and mutual support. The trio openly acknowledged that individually, each lacked sufficient strength or durability to confront such opponents alone, relying entirely on unity. Their primary fighting style integrates varied martial arts techniques adapted to exploit numerical advantage and cooperation, specifically employing boxing against Iron Michael.

However, their cohesion is their critical weakness—incapacity of any member disrupts their effectiveness. This flaw was exposed when Jun Guevaru intervened: one member was physically overwhelmed, another fled in terror, and the remaining retreated, abandoning their objective. The Mouth operates with shared confidence and intelligence, leveraging practiced martial arts to predict and complement each other's actions. Their effectiveness diminishes drastically if any member is removed. Their history centers on the Great Prison Battle Saga, where their coordinated assault initially succeeded against Iron Michael but ultimately failed due to Guevaru's intervention and their subsequent loss of unity.