[He's very curious about it, yes!! Curious and thankful Katsuki's talking at all, honestly.
Not that he'll make that obvious in the least.]

... Y'all both stupid. But in a good way.
You two're gonna be tighter than a rubberband ball once ya get past the awkward "talkin' it out" part, I can tell ya that right now.

["Stupid in a good way" meaning "It sounds to me like you're both crushing, please just tell him, stop being dumb". Of course.]