Mametchi is a highly intelligent and inventive character whose deep fear of the dark stems from a traumatic childhood incident where he was trapped in a dark place. This fear drives him to invent the Transporter Machine, aiming to bring a private sun for constant light; however, it accidentally transports a human girl named Tanpopo to Tamagotchi Planet instead. He demonstrates responsibility and care, especially when watching his family's egg. After the egg rolls away into danger, he acts immediately to rescue it, showing bravery despite his personal fears. The successful rescue and subsequent hatching of his sister ChaMametchi highlight his protective nature. His inventive dedication leads him to create "Mamesunnytchi," a miniature sun companion, but this inadvertently causes Tamagotchi Planet's sun, Sunnytchi, to depart, triggering planetary illness. Mametchi blames himself for this catastrophe, revealing his tendency toward self-reproach. During the stressful space mission to find Sunnytchi, Mametchi loses his temper with ChaMametchi, chastising her for interfering, which exposes his struggles with sibling dynamics and responsibility. He later reconciles with her, admitting his harshness and showing his capacity for growth and empathy. A pivotal challenge arises when confronting a perceived black hole—the entity Blackholetchi—forcing him to overcome his paralyzing fear of darkness to save his friends. His active participation in efforts to awaken Blackholetchi marks a significant personal triumph. Mametchi's character arc concludes with renewed maturity after Sunnytchi returns and explains the absence was merely a vacation, giving him perspective on his guilt. His experiences throughout the journey forge his role as a dependable older brother and problem-solver.