"Rui is one of the main characters in the Japanese manga series ""It's Mine."" She is a high school student who attends the same school as the other main characters, Kazuto and Rio.

Rui is portrayed as a strong-willed, confident, and independent person. She has a no-nonsense attitude and isn't afraid to speak her mind, often standing up for what she believes in. Despite her tough exterior, Rui is also shown to be caring and compassionate, especially towards her friends.

Rui has a close relationship with Kazuto, although it is initially portrayed as one-sided. She has strong feelings for him but is hesitant to confess her love. This adds to her character's complexity, as she struggles with her own emotions and desires while maintaining her image of strength and independence.

Throughout the series, Rui is shown to be incredibly intelligent and resourceful, often coming up with solutions to problems that the other characters overlook. She is also a talented martial artist and has a black belt in karate, which empowers her to defend herself against any attacker.

Overall, Rui is a multifaceted character who adds a lot of depth and intrigue to the story of ""It's Mine."" Her strong personality and unique interests make her stand out from other female characters in the genre, making her a beloved and memorable addition to the series."