Original female protagonist, no CP
The protagonist was born into a noble family entrusted with guarding the sacred artifact "Yata no Kagami Sword." Aizen destroyed her family, and Squad Zero drained all her spiritual power to seal the artifact, leaving her with amnesia and the body of a child.
But she's determined to make the best of it! Cursed with the fact that "her spiritual power makes it impossible for her to become a Soul Reaper," she keeps fighting back after every defeat, transferring from Squad Four to Squad Six and then Squad Thirteen, and even becoming an officer!
Aizen: It's getting cold. Time for the Soul King's right hand to go.
On the night of Kaien's death, the protagonist has her heart pierced by a shot from Gin Ichimaru and becomes a 100% pure-blooded Adjuchas. From then on, she swears eternal enmity against the Soul Reapers.
--Soul Reapers? Aizen, I'm done being human!