Kairi is a central character in the Kingdom Hearts series, known for her kind and caring nature. She is one of the seven Princesses of Heart, pure-hearted maidens required to open the Door to Darkness. Kairi originates from Radiant Garden and is one of Sora's closest friends, along with Riku. Throughout the series, she plays a crucial role in motivating Sora on his journey to save the worlds from darkness. Kairi's deep bond with Sora and her eventual development as a Keyblade wielder highlight her importance in the overarching narrative.