Tsukuyomi is a Shinmei Ryuu swordswoman first appearing as one of three mercenary children hired by Chigusa. She fights with a sword and dagger, contrasting Setsuna's single-sword style. Tsukuyomi also wields onmyoudou magic, skilled with ofuda charms like Setsuna. After Chigusa's defeat, she returned to her place of origin. She later emerged in the Magical World as a covert agent in a squad under Fate Averruncus. Her mission involved framing Negi Springfield's Mahora team for destroying the gate linking the human and Magical Worlds. Tsukuyomi has blonde hair, wears glasses, and bears a notable resemblance to Toko, suggesting a possible familial link. Outwardly relatively innocent, Tsukuyomi reportedly enjoys combat intensely, sometimes displaying bloodlust and tormenting opponents. Subtext suggests an unconfirmed underlying affection or crush towards Setsuna. She favors Gothic Lolita fashion. Later, Tsukuyomi finds Setsuna and Asuna defenseless in another Magical World region, hinting at potential narrative re-engagement. In the broader continuity extending into *UQ Holder!*, Tsukuyomi Iwai is confirmed as the same character, appearing in Fate Averruncus' Ala Alba group, explicitly stated by creator Ken Akamatsu. Her affiliations shift from Chigusa to Fate Averruncus' forces, indicating recurring roles within antagonist-aligned groups across arcs.