Musubi is a sekirei, a race of super-powered humanoid aliens, physically indistinguishable from humans with similar genetic codes.

Long ago, 8 Sekirei spaceships reached Earthm with each ship containing 108 life-forms described as "One pillar & 107 baby birds". One crash-landed & suffered severe damage; only the "Pillar" & 8 Sekirei survived. Another, the one which carried the "modern" Sekirei, crashed in the sea near Japan. The rest landed in various locations worldwide, & the Sekirei aboard them gave rise to the myths & legends of gods & heroes that have passed down through various cultures over the span of human history.

One dau, an island emerged suddenly from the sea near Japan; it was quickly explored by 2 university students, Minaka Hiroto (future MBI chairman) & Takami Sahashi (future MBI head researcher). They discovered ruins which were actually the 8th Sekirei spaceship. Onboard the spaceship they found 108 life-forms in suspended animation:

The first of them, the pillar, shown as #01 was an adult, & was not a Sekirei. 8, later known as #02-09 were embryos & the 99 others known as #10-108 were fertilized eggs.

Minaka used the high technology discovered on the Sekirei ship to amass the fortune required to found MBI, take possession of the island & have it declared an extraterritoriality. He then began the work that would eventually result in the Sekirei Plan.

Musubi is a close-combat sekirei with fair-skin, brown hair & brown eyes. She has a slender build & a very developed, curvaceous body with a slim waist & flared hips. Her sizes being B97/W58/H89.

She wears a white gi with a pink waist sash & a short red pleated skirt. She also wears a pair of mid-calf brown boots, thigh-high white stockings & red combat gloves.

Musubi is very cheerful & carefree to the point of not having any concept of modesty, as she routinely appears either under dressed or with little or no attempt to cover her exposed breasts. She is very naive, but insightful, often saying things she does not understand.