What is musubi?

Some articles on musubi:

List Of Sekirei Episodes - Episodes - Sekirei: Pure Engagement (2010)
... Meanwhile, Benitsubasa plots her revenge on Musubi 02 "The Wind Blows" "Kaze Tachinu" (風立チヌ) July 11, 2010 Tensions in the city continue to escalate ... alone, Benitsubasa captures Minato in an attempt to draw Musubi out and into a fight ... Musubi and Tsukiumi arrive and take Minato to the hospital ...
List Of Sekirei Characters - Mid Bio Informatics - Discipline Squad - Current Members
... when she killed a numerous amount of soldiers during her mission to rescue Musubi ... She maintains a "friendly" relationship with Musubi (whom she calls "Mū-chan"), and the two have made a promise to be the last two Sekirei standing ... Like Musubi, she is a hand-to-hand fighter, but as stated by Haihane they are complete opposites ...