he probably thought the idea over for a while before he brought it up - savouring it, like, turning it over from every angle - yep, it looks that way too! yeah, it still looks good! so by the time he finally proposed to nino, he'd worn the idea completely familiar in his head and it didn't really seem that surprising anymore. nino is surprised, of course (even though it is ohno - maybe he just kind of stares at him for a second, blinking), and that surprises ohno.