As a child, Sachi lived with her parents who adopted Rumi Igarashi into their family. Rumi was eventually sent away due to an incident and her haughty behavior despite Sachi's affection for her. Sachi harbored a regret for not being able to save Rumi when she was sent away. Upon learning of the WIXOSS battles, Sachi acted upon her wish to save Rumi and became an LRIG. She initially failed in fulfilling her wish but thanks to the efforts of Ruuko Kominato she is eventually reunited with Rumi who had also become an LRIG, Ulith. She vows to forever stay together with Rumi so that the latter will no longer be alone. Sachi met Ruuko in their childhoods and gave her the nickname, Tama, whom the latter would then give as a new name to Shiro.