Second in command on the Tenshin crew, Koemi is a free-spirited, charismatic woman with a flirtatious mindset toward people like Isshin and sometimes Jayson. Growing up with no family or loved ones, at the age of 16 to 18, Koemi worked in the Red Light district in Japan to survive. During her work, she fell in love with a man who took her out of that district to live with him. After a few months of dating, she found out she was pregnant and wanted to surprise her boyfriend, only to find out he was murdered by one of the Kemuri members, staging the crime scene as a home invasion.

This took a mental toll on Koemi and a month later, she suffered a miscarriage. Although her boyfriend left her enough money to live before he was killed, Koemi knew he couldn't stay in his apartment for long. Considering going back to the Red Light District, she used most of the money to get her tubes tied to prevent her from getting pregnant again and save the rest of the money for later. While going back to the Red Light District, she was attacked by one of the Kemuri members who killed her boyfriend. Unbenounce to her, she develops the Soul Ki which contains the elements of Summer. Unfamiliar with her powers, watching her from afar, Chiaki came in to save her from the Kemuri. With no left to go, Chiaki kindly took her in to understand her newfound powers and became a member of the Tenshin Clan.