Hagi is a gray anthropomorphic cat with blushed cheeks, dark gray limbs, and a red star marking on the right ear. A red bow adorns the neck, contrasting with the left ear's dark gray hue. These features differentiate Hagi from twin Tsugi, who displays a head bow and dark gray right ear.

Crafted by Yuni—a being born from loneliness after falling from the sky and receiving life from the Queen of Nightmare—Hagi emerged as a patchwork plush companion alongside Tsugi. Both gained sentience and speech shortly after creation to alleviate Yuni's isolation. Their combined names form "tsugihagi," meaning "splicing" or "patching," echoing their stitched origins.

Hagi speaks with sentences ending in "~hagi," mirroring Tsugi's "~tsugi" pattern, reinforcing their paired identity. Initially, they assist Yuni in spreading "Black Abysses" to disrupt human dreams under the Queen of Nightmare's command, demonstrating unwavering loyalty to Yuni. This allegiance extends to Yuni's partners: first Haruhito Sugiyama, then Akihito Sugiyama.

In *Mewkledreamy Mix!*, leadership shifts as Akumu replaces the Queen of Nightmare, becoming Hagi and Tsugi's direct supervisor and altering their duties. Their core bond as Yuni's creations remains unchanged throughout this transition.