Yumi is a former hostess at the Serena Bar and the sister of Mizuki.
Born on 30th June 1971, Yumi was a close friend of both Kiryu and Nishiki whom she met at the Sunflower Orphanage. She is younger than them and pampered by both boys and Kazama as well. After Kiryu's and Nishiki's departure from the orphanage, with kazama's assistance, she too left the place and graduated from junior college, living a life of independence. In order to base in the location where her close friends were, she left for Tokyo and started working in Serena as a hostess. There, she builds a trusting relationship with Reina, the bar's mama-san. Life was smooth sailing then for her until an event took place in 1995.
Yumi was never the same after the event at Dojima's office and disappeared from the hospital immediately after. She drifted apart from her two best friends.
She didn't know that Kazuma thought about her constantly and Nishiki carried her ring in his pocket after finding it that fateful night. She went to work as a hostess in Reina’s popular Serena Bar though she remained quiet and withdrawn.
One day her sister, Mizuki, disappeared and from then on, Yumi spent most of her free time with her niece, Haruka, at the Sunflower Orphanage. That is, until she vanished. She is Kazuma Kiryu's childhood love and best friend Nishiki's fiancée, while the father of her child was Jingu, the head of the MBI.