DISCLAIMER: I don't own Bleach. And I am not a natural English speaker, so beware of the grammar errors that you might find.
LOOP.
It wasn't precisely something that he could treasure. It was something vainer. As if she wasn't even there… At that moment he remembered that she was not a complete human anymore, no, she was a shinigami. And that was the reason of why he had always let her go. Because it was not meant to be and yet... and yet…
Here he was with her sharing a bed. Making love to the only woman that he had loved.
And then she would leave. With a broken heart. With a ray of faith.
He didn't want anyone else. No one but her. Why was it that he kept looking for the things that he couldn't have? Was it destiny something so cruel as to let them together only to make them brake once and again and again and again? How many times had she got hurt? By him nonetheless… by saving him? Was he even worth it of her? Was he good enough? He could have everything to make his life complete. In the perspective of someone else that is. Does he not want to be happy? Of course he does want to be happy! But happy was nothing compare to the feeling she gave him.
And so he wanted more. More than just an illusion. More than just fights and lost and despair. More than just mere encounters for very brief moments. He wanted a life with her.
Substitute? No. He was more. He deserved more! And so he became more. And when he got the chance he gave away his life in order to revive by her side. It didn't matter that he had to start all over again. Because that meant more days with her. It didn't matter that he have to chase her all over the place, because it made him excited, because it gave them more time to be one. To lose themselves in a different kind of fight. To be something that they couldn't have ever been if he had stayed alive…