Shizu Onuma descends from a family with generations-long allegiance to the Makishima household. Her grandfather, Yohei Onuma, was a devoted retainer to the Makishimas who raised Shizu following her parents' unexplained disappearance. This upbringing forged her absolute loyalty to Agito Makishima, whom she met in his youth and whose objectives she places above all else. Naturally gentle and kind, Shizu transforms into a dangerously ruthless operative when executing Agito's will. Her devotion drove her to volunteer as the first female Zoalord, undergoing Alfred Hekkaring's processing to become Griselda and advance Agito's ambitions for the resistance faction "Zeus' Thunderbolts." As Griselda, she commands the Libertus—Zoanoid soldiers engineered to resist Cronos' psychic domination. Her powers include directing Libertus forces in battle, blocking other Zoalords' command waves, and healing grievously injured Libertus members through touch. Her Zoalord form wields two razor-sharp, sheet-like head blades that drape like hair or a cape but unleash lethal spinning attacks. She possesses superhuman strength enabling combat with Guyver II-F, reflexes and speed rivaling Guyver units, and extreme durability that allows survival despite catastrophic injuries like severed limbs. The Zoalord transformation drastically shortens her lifespan, a cost she accepts for Agito's goals. Their relationship carries spousal undertones. After Cronos' global takeover, Shizu remains Agito's strategic asset within Zeus' Thunderbolts, opposing Cronos' dominion.