Miyu, designated the Merciful Intelligential Yggdrasil Unit, possesses an extended operational lifespan spanning centuries, potentially originating from the War of the 12 Kingdoms. This longevity provides her with vast historical knowledge, though she acknowledges gaps exist. Her core directive is fulfilling the final wish of her original companion, Alyssa: monitoring and safeguarding the world's future inhabitants, particularly those connected to the fate of Otomes and the stars. She exhibits a protective instinct towards Alyssa's descendants, recognized by a distinctive golden glow.

In *My-Otome 0~S.ifr~*, Miyu intervenes in a confrontation between Elliot and M9-R, attempting a rescue but being impaled and temporarily deactivated. Found later in a petrified state near a crater, she is restored and urgently warns Shizuru Viola to flee a shadowy entity capable of mimicry. This entity later imitates her appearance to infiltrate Garderobe. The petrification resulted from the enemy solidifying nanomachines within Otomes. Miyu returns to functionality after the defeat of Yuna.

Her capabilities include deploying the specialized Mythril Dress combat suit, retrieved from a lava pit, and wielding the anti-materialization weapon "Sword Marie." This weapon upgrades to "Artemis" by channeling the essence of Alyssa through her companion bird, demonstrating power sufficient to counter threats like the Ultimate Black Diamond. Miyu also activates the Guiding Star system, temporarily suspending Otome contracts globally during conflict.

Across other media like the *My-Otome* manga, she is identified as part of the MAID series (Multi-purpose Assistant-type Independent Droid). Excavated and restored by Alyssa Kruger, a later gravitational struggle restores her suppressed memories, unlocking an advanced form of her Mythril Dress enabling her to defeat adversaries like Alyssa Searrs. Her design consistently features sleek blue hair, red eyes, and practical attire including a hat and cape.