Mini initially deemed Kazuya as a playboy for renting a girlfriend while he has a (temporary) girlfriend. On a certain day, she took Kazuya by force to her room to learn more about his weird relationship.
After Kazuya was forced to tell everything because she had the clash conversation between Chizuru and Ruka, Mini was deeply moved with his story. It leads Mini to deem Kazuya as her master and promise to help him with his current life. Mini selfishly becomes a cupid for Kazuya to have Chizuru as his real girlfriend later.
Chizuru was initially wary with Mini because she knows her secret relationship with Kazuya. Despite this she is glad that Mini had decided to keep the secret, it annoys her more that Mini secretly became a servant. But unknown to her, it also means to be the cupid to help Kazuya.
Ruka initially disliked Mini as she deemed her as another love rival to be with Kazuya. While initially relieved that it won't happen, it ticked her when Mini claimed herself to be Kazuya's self proclaimed servant. Mini was even brave enough to set up Ruka to be apart from Kazuya and Chizuru, which completely pissed Ruka off.
Mini is acquainted with Shun through a friend of hers, much to Kazuya's surprise. Due to the honorifics used and inside jokes, they appear to be good friends.