Riasu Tatsuno, known as Reese Drake in English adaptations, is the older sister of Zoe Drake and a vital scientist within the D-Lab team. Serving primarily as Dr. Spike Taylor's assistant, her exceptional organizational skills and serious nature often position her as the de facto head of the lab. She possesses advanced expertise in robotics, information technology, and paleontological research. Her key inventions include the Dino Holders, enabling the D-Team to activate and communicate with dinosaurs, and the later DinoShot device from the DS game, which streamlines card activation and allows her to monitor the Alpha Gang for strategic player updates. Beyond the lab, she holds a pilot's license and operates her own aircraft for field missions.

She has long blonde hair, typically worn in braids or with a hairclip, purple eyes, and wears square-framed glasses so integral to her appearance that others find her unrecognizable without them. Her standard attire is a green top, brown miniskirt, white lab coat, and dark red high heels.

Predominantly calm, reserved, and monotonic in speech, she rarely displays overt emotions, even under stress. This stoicism is occasionally broken by intense but controlled anger, manifesting as "silent fury" – demonstrated when she physically restrained Dr. Taylor with surprising strength. She enforces strict cleanliness and order in the lab, showing impatience with frivolity and typically ignoring Dr. Taylor's jokes. Despite her stern exterior, she exhibits deep protective loyalty towards her sister Zoe, confronting threats like Seth's Cryolophosaurus. Her professional relationships include coordinating with Rex Owen on technical matters, managing Max Taylor's impulsiveness, and tolerating Dr. Taylor's eccentricities while respecting his scientific passion. Zander of the Alpha Gang develops a romantic interest, serenading her and offering gifts, but she remains largely indifferent to his advances and fails to recognize him without his sunglasses.

Her role evolves across the series. Initially focused on technological support and lab management in the first season, she remains at the D-Lab coordinating efforts with Rod and Laura during the second season's conflict with the Spectral Space Pirates. Seth later takes her hostage, threatening her with his Cryolophosaurus to force the D-Team's surrender of the Cosmos Stones; she maintains composure and provides strategic assistance throughout. She also performed partial repairs on the futuristic android Jonathan, though the complexity of his design prevented full restoration.

Trivia includes her love of cake, her occasional attire changes (uncommon among main characters), and a canonical mention that she never had a boyfriend. Her Japanese name, Tatsuno Riasu, incorporates the word for "dragon" (tatsu), reflected in her English surname "Drake"; her Taiwanese localization name is Liz.