You've just paralyzed me with joy. There's so much more to Kazuki than girly-whirly fabulousness and nurse costumes; he's not overtly angsty, but there's so many layers of grief and regrets to his character. I appreciate that you portray him as loving Juubei deeply, yet yearning for something more.
The line about refusing his ally and letting the rejection poison them both especially struck me. I think that Kazu-chan is a master of gently saying "no," but that it still stings him every time.