After her loss to Kiba in their master's rating game, she developed a huge crush on him to the point of Tsubaki losing her usual calm demeanour when in front of or at the mention of him.
Because of the deep fraternal relationship that Kiba and Issei share, Tsubaki sees Issei as a potential rival thus making her one of the many girls that believe in the rumors of a homoerotic relationship, something that greatly annoys him. In spite of this, Issei is supportive of her efforts to romance Kiba, if only to dispel the rumors.
Tsubaki is Sona's Queen and is commonly seen in Sona's side. She is one of the few people to truly understand Sona.
As an old friend of Kiba's, Tsubaki views her as rival although Tosca herself is unaware of this.