Mimi Usa is a key character in the anime series 'Kodomo no Jikan.' She is a shy and introverted girl who is best friends with the main character, Rin Kokonoe. Mimi is known for her intelligence and sensitivity, often acting as the voice of reason in her group of friends. Despite her timid nature, she deeply cares for those around her and often struggles with her insecurities. Her character arc deals with themes of friendship, personal growth, and overcoming emotional challenges, making her an integral part of the series' narrative.