My guess? Reality came back with a vengeance. Ragna might have long resigned himself to it, but he never did like having to murder those wearing his sister's face, and for all her insanity, Nu genuinely cared for him. Hell, I am under the impression that Nu wants the world to burn in retaliation for all the crap Ragna has been put through as much as it is her insane desire to destroy and "be together" with him.
Remember how happy she was while in Lambda's body because she was able to protect him even as she died in his arms?
My guess? Reality came back with a vengeance. Ragna might have long resigned himself to it, but he never did like having to murder those wearing his sister's face, and for all her insanity, Nu genuinely cared for him. Hell, I am under the impression that Nu wants the world to burn in retaliation for all the crap Ragna has been put through as much as it is her insane desire to destroy and "be together" with him.
Remember how happy she was while in Lambda's body because she was able to protect him even as she died in his arms?
According to Kuro Yuzu, this comic is based on Phase Shift 0.