[This kind of narrow, determined reliance probably isn't very good for either of them in the end - it certainly has the strong potential to become unhealthy, anyway - but Kashuu needs someone to lean on about as much as he needs others to need him. He's not a human with the mentality of an object as Souji is; he's an object trying to learn how to view himself as something slightly more human, and that's difficult in an entirely different way. He just can't divorce himself from the notion that he should be of use, that he should be necessary, and the only thing that he was taught about importance is that he has to strive for perfection because anything less gets scrapped.

In the same way that Souji feels like this is a betrayal, Kashuu isn't entirely happy with it either. After all, he'll have to go back home sooner or later. Once he's there, he'll need to ensure that Souji dies over and over again, no matter how many times they have to go to the past or how many times this Souji tells him in the present that he's loved. Open affection in this situation is, quite frankly, not well-suited for his line of work.

...But he only smiles in the end, a quick burst of happiness on his face before he tries to tamp down on it again. The reassurance is too nice to let go of for now.]

Eh, seriously? [Refocusing on the conversation and sounding mildly incredulous! If it weren't for the ENTIRE AWKWARD AIR they're facing, he'd probably make a joke about being hurt that he wasn't the first, but no... Instead:]

I guess that's not too surprising. I mean, even a prodigy can't pick a sword up and use it as well as you used me. Not that fast, anyway.