Suruga is Koyomi and Hitagi's underclassmen and is the ace of the basketball club at school. She has known Hitagi since middle school.
Suruga is a character from the Monogatari franchise and has made appearances in the light novel series written by Nishio Ishin, featuring illustrations by Vofan, and published by Kodansha. She has also made appearances in the anime series based off of these light novels: Bakemonogatari and Nisemonogatari, both of which are produced by Shaft and published by Aniplex . Her original design is credited to the writer and illustrator of the light novel series while her anime appearance is credited to Akio Watanabe. She makes her first appearance in Bakemonogatari #6.
Suruga's tale begins one day when she found a mythical monkey's paw in her folks' old home. Because she was trying out for the track team, she wished the monkey's paw would make her go faster. However, four of the students who also tried out for the same team died under mysterious circumstances. Suruga told Araragi that her wish to the paw held consequences she didn't imagine, so she instead transferred to the school's basketball team, thinking that if she didn't encounter anyone faster then the monkey's paw wouldn't cause their deaths. Sometime after this event, when she looked for the monkey's paw to cast another wish, the paw had grafted itself onto her left arm.
While playing on the basketball team, she met Senjogahara for the first time. She began to develop feelings for her, as she tells Araragi that she is a lesbian. However, Senjogahara didn't seem to reciprocate those feelings, so Suruga forced herself to settle for being "just friends" with Senjogahara. Even so, she kept up her work with the basketball team, and practiced her running every day. Then sometime later, she caught Senjogahara and Araragi being flirty with each other, and she grew jealous that she would fall for a guy just like that when she had shown her affection for a few years. As a result, when Araragi is walking home one night, Suruga's monkey arm punches a hole through his torso, but Araragi manages to survive with his vampiric healing powers.
When Araragi takes her to see Oshino, Oshino replies that it is not just a normal monkey's paw, but a demonic presence that is tapping into her subconcious to grant her deepest desires, desires that apparently involve murdering people. Oshino then tells the two that if Suruga wants to get rid of the demonic curse, her only two options are either chopping off the whole arm, or letting her kill Araragi to fulfill her last wish. Araragi ends up fighting her in an enclosed room, and Suruga literally paints the walls with his insides, but Senjogahara arrives on the scene to talk her down and bring Suruga back to normal.
Nowadays, Suruga treats Araragi as a good friend, even helping him with the Nadeko case.