Rika Ueda, a 13-year-old middle school student unenrolled at Seitetsu Academy, maintains connections to the institution through her older sister Makie Ueda, who attends Seitetsu Gakuin Class 5. She possesses distinctive pink hair and pink eyes, typically clad in a black school uniform. Her path as a fighter began accidentally when she received a Messenger animal doll, originally sent to her sister by Kaede Sakura. This event transformed her into a White Kämpfer.

Functioning as a Schwert-type Kämpfer, she specializes in close combat wielding a kusarigama—a sickle-and-chain weapon. Her unique variation features weighted components on the chain ends instead of blades. As the smallest member of the White Kämpfer faction, a third group formed after the Red and Blue factions ceased hostilities, she engages opponents by whirling her chains.

Her personality reflects inexperience and youthful arrogance, drawing parallels to Shizuku Sangō though her combat effectiveness remains lower due to limited experience. She also exhibits a playful and cheeky demeanor within her group. Her sole documented combat action occurred during a sleepover at Kaede's residence, where she intervened to block an attack by Shizuku Sangō, though her efforts proved ineffective.