Rin Onigawara/Relationships

Parents
Rin has a complex relationship with her parents. As a young child, her father had an affair and abandoned their family. Her mother was devastated by the divorce and would take it out on Rin by scorning her as the child of a demon since she resembled her father, forcing her to wear a mask to even interact with her. Despite this emotional scarring, Rin still loves her mother and doesn't seem to hold any resentment to her. While not confirmed, it is likely her father's actions to their family is what caused her to detest men since she experience a painful life as a child. It is unknown whether she still loves her father or if she still speaks to him after her childhood.

Fudou Nomura
At first, Rin saw Nomura as a delinquent and wanted to correct him like the other boys in the school. When he refused, she battled him but was defeated as a result and felt humiliated when they accidentally kissed each other.

Following their next meeting, it appears she now held feelings for Nomura as she was flustered by his words about the kiss blushing profusely even more so after he stated his desire to see her in regular clothes. When he hangs out with other girls, she is often shown to be very jealous.

When Satori framed him, making it seem like he indecently slept with her, Rin cried in anger and violently tortured him. When she learned from Satori that he was framed, she was overcome with remorse and even let him remove her mask as "his punishment" for her actions.

She appears to trust him very deeply, as she was willing to explain her reason for wearing the mask is due to her mother taking out her anger on her due to her father's affair and abandoning them. After hearing the story, he returned the mask and told her to wear it if it makes her feel better. In this moment, the depths of their bond was truly shown as he confided in her of his own tragic past of being an orphan and dealing with his abusive grandfather who was his guardian.

Mary Kikakujou
Mary is one of her colleagues in the Five Swords. It is shown that both share a dislike of men and have resorted to "correcting" their actions so the school could better function. Out of all the members of the Five Swords, Mary is the one that Rin has the most interactions with.

They get along fine and respect the other's skill however, both girls share a romantic interest in the same boy. Because of this, they both compete over Nomura's affections and Rin gets annoyed by Mary's perverted desire of Nomura subjecting her to some weird treatment while she suspects he does so to Rin. When it comes to it, they will unite as shown after they both tortured Nomura or when they both fought off Kirukiru Amou.