Tsukino, a member of the Tsukinowaguma bear species, serves as keyboardist and vocalist for Criticrista. Raised in the remote mountains of Dai Mountain before attending St. MIDI Girl's Middle School, this isolated upbringing fostered significant naivete about the wider world, contributing to her childlike, often ditzy personality and a habit of referring to herself in the third person. She participates in the Student Council's Beautification Committee but struggles with finances, once diverting committee funds to buy snacks instead of necessary supplies like copy paper.

Her defining characteristic is an intense obsession with food. She frequently discusses meals, employs food-based analogies, maintains a daily-updated food blog, and becomes visibly distressed if her food spoils or goes to waste. This preoccupation leads her to daydream about food during idle moments. Despite consuming large quantities, she exhibits no weight gain, showing specific preferences for red bean paste, strawberry anmitsu ice cream, matsutake mushrooms, and raw meat.

Physically, she has dark blue eyes and semi-curly sky blue hair featuring a pastel yellow moon-shaped ahoge. Her standard attire is a custom sailor-style uniform consisting of a blue crop top, white gloves, a blue scarf fastened with a gold-and-blue spade brooch (her symbolic motif), burgundy stockings, and white boots decorated with spade accessories. She possesses multiple alternate outfits: a grape-themed dress with a frilly apron, a Setsubun-themed oni costume complete with a kanabo club, a tankini swimsuit with hibiscus hair accessories, and a lolita-inspired dress with rabbit ears for moon-viewing ceremonies.

Her mountain background granted her exceptional abilities: perfect pitch and superhuman strength, the latter demonstrated when she punched a wild bear. These traits enhance Criticrista's musical performances. She interacts with fans by calling them "oniinii" (big brother) and "oneenee" (big sister), while her fans refer to her as "Tsukino-taso" and respectfully avoid disturbing her during meals or rest.

Her name originates from "tsuki no waguma" (Japanese for Asian black bear), aligning with her species. The moon-shaped ahoge and cream-colored chest marking mirror real-world "moon bears." Additional quirks include substituting a cinnamon roll for a meat bun in certain costume animations and evolving home screen dialogues where she expresses cravings for specific foods like grilled mackerel or meat during autumn leaf viewing.