Adelheid's more than a little wary of Okita. From what he's seen, Okita is dangerous and yet hides it beneath a facade... neither of which bodes well in his experience.

Whereas Alfons thinks Ritsuka is cute and yet has a very sad past, something that he can sympathize with. He wants to make memories with Ritsuka, so that neither of them will really disappear... and he hopes, although it's tremendously unlikely, that someday he can show Ritsuka that he's not just a replacement. He doesn't want anyone to feel like that, ever.