Karen Amagase (天ヶ瀬=カレン, Amagase Karen) is Gai Nagareboshi's adoptive mother and a former member of the Gotei 13 before deserting Soul Society's laws for a more peaceful life. Several thousand years ago, Karen was known as Wakana Yoshi, a lieutenant of the Gotei 13. She was forced by the then current Captain-Commander to assist him in defending Seireitei from the "Sōrai no Kishi", meeting a younger Mitsuru Inazuma in the process, with the two developing a close bond. After Central 46 ordered the Royal Guard to slaughter Mitsuru and his companions, with Karen only barely surviving due to the unexpected assistance of Nika, who used her memory manipulation to wipe the Central 46, Royal Guard, and the Gotei 13's memories of "Wakana Yoshi", allowing Karen to take upon a new name and begin anew.