Masha presents as a small, round, pink robotic creature covered in soft fur, featuring prominent cat ears, large pink eyes, and a permanent blush-like appearance. Designed as prototype R-2000 by scientists Ryou Shirogane and Keiichiro Akasaka, he earned his nickname from Ichigo Momomiya as a playful nod to her boyfriend Masaya Aoyama. This designation sets him apart from the later Ucha model (R-3000). Though originating from Mia Ikumi’s *Tokyo Black Cat Girl* one-shot as a fully verbal intergalactic police officer with flight, repair, and memory-erasure capabilities, Masha’s functions and personality were redesigned for the main *Tokyo Mew Mew* storyline.

In this continuity, he communicates primarily through sounds like "pi" or "tweet," speaking only one complete sentence in *Tokyo Mew Mew à la Mode*. His core programming detects distress signals, Chimera Anima threats, and Mew Aqua energy. During battles, he consumes defeated Chimera Anima—calling this "Collect!"—to prevent their revival. He also fuses with Mew Aqua to form the Mew Aqua Rod, enabling the Ribbon Aqua Drops healing technique. Despite minimal combat prowess, Masha fiercely supports Ichigo, often diving into conflicts to aid her.

After the aliens’ defeat, Masha accompanies Ichigo to London with Masaya, leaving a narrative gap filled by Ucha’s introduction for Berry Shirayuki in *à la Mode*. He returns in the 2022 reboot *Tokyo Mew Mew New*, maintaining his protective duties and signature skills. Internationally, localized names include "Mini-Mew" (4Kids English), "Mini-Gatinha" (Brazilian Portuguese), and "Mini-Mjau" (Albanian). A publishing anomaly occurred when Tokyopop misgendered him as female in one manga volume, contradicting his consistent male portrayal in Japanese media.