[It's not exactly any one of those that he means, not that it helps any. Just that Kamui's idea of his confrontation with Seishirou was very different from what had actually happened now by Kiseki's hand. Especially as he had come to realize over the recent years...]
[We were supposed to run away. You were supposed to forget him. Killing him was supposed to be the easy part if he ever found them again-- all of those thoughts had always gone through his head, but mostly now there's the fact that he knew since the past few years the more they ran, the less Subaru forgot, the less his connection to the hunter faded. Part of Kamui had come to realize that in the end, yes, it was either going to be him or Seishirou to die, but that perhaps they would simply destroy each other.
More and more... Subaru's sad eyes remind him that he almost wished for the last option just so he didn't have to see him like this at the end of it.]