KInji Tohyama was Kikuyo friend while at Kanagawa Butei Junior High, who stood up for her from bullies and from being accused of any wrong doing. However, she find out about his Hysteria Mode abilities and how to use it make him her "Ally of Justice," which caused him to dislike girls and for her to later feel sorry about. At one point she had fallen in love with Kinji even tried multiple times to give him a love letter, but destroyed it each time due to feeling guilty about her actions. Even after leaving Kinji to become head of her family syndicate of the Yakuza, she always wanted to see him again.
When she met Kinji again after his fight with Leon, she felt very happy to see him again to the point where her heart was beating fast and even tried to get to join the her family as her boyfriend and later wife, which he turned down. Then during Kikuyo henchmen coup e'tat, Kinji managed to get her and Moe to safety while GIII and Aria were dealing with the Yakuza, but they came back with Kikuyo willing to die in order to protect Kinji and apologize for her past actions, but was saved by Kinji. After the incident was over, Kikuyo took a plea bargain, paid bail, and sent an e-mail to Kinji indicating she was lonely and wanted to see again. Later on, she decided to enroll in Butei High to get closer to him.
Kikuyo relationship with Moe Mochizuki started rough and aggressive due to kidnapping and holding her hostage in order to lure Kinji back after refusing Kikuyo offer and for having grudge against each other for Kinji's affection. However, there relationship became more friendly after Kikuyo henchmen overthrew, they both prayed to a star (Aria) for Kinji to be saved and were willing to come back from safety in order to defend the man they both love, Kinji. After Kinji went back to Butei High, Kikuyo and Moe conspired together in enrolling into the school to follow Kinji.
Master Kou was Kikuyo contact from Ranpan as part of their business deal the Kagataka Family Syndicate until syndicate was disbanded.