Imperial Premier of Yamatai, sister of Ketsurui Yui, and former Empress of Yamatai Star Empire, Yuumi is one of the oldest Nekovalkyrja.

Yuumi was raised by Ketsurui Uesu to be Empress, and he abdicated the throne to her. She was killed in an Elysian attack that destroyed the old capital of Yamatai, Geshrinopolis. Eve recreated Yuumi using a secret mental backup and held her hostage for several years, using her access to manipulate the PANTHEON system. Luckily for Yuumi, she was recently rescued by the crew of the YSS Sakura. After recovering from her severe mental duress at the Empress' Palace in Kyoto, she became politically involved again in YE 33, when she agreed, for the good of the Empire, to serve Empress Himiko I as the Imperial Premier.

In YE 43, Yuumi decided to retire early from her role as Imperial Premier¹⁾.

Yuumi stands 5'1“ (155 centimeters). She has the athletic, slim frame typical of her species, though her backend has a bit more heft to it (she does squats each day). She keeps her teal hair close to the usual princess cut, though she has her bangs parted and swept off of her forehead and out of her eyes. Her face is long, cheekbones high and neck slim. She has a modest, pert bustline that rests below rather broad shoulders. Those shoulders are proportional to her hips, with a narrow waist between them. She has slim, muscled legs that she keeps in good shape.

Yuumi is most at home wearing a tailored women's pantsuit, though she wears a kimono for formal occasions and dresses for off-duty ones. Her favorite dress is a backless, black cocktail dress that skips just below her knees, with a pencil skirt bottom. Her favorite kimono is cream-colored with red-pink trim and flower designs and a grey-white obi.

• Unfired Missile (YE 44 Salvage Giveaway, TC: 26-42, IC: 1123-20637-65)
• Large box full of towels (YE 44 Salvage Giveaway, TC: 58-40, IC: 2319-19697-92)
• Medicines from a ship's medical bay (YE 44 Salvage Giveaway, TC: 85-53, IC: 4477-26133-128)