In Episode 2 of Tonikaku Kawaii (Fly Me to the Moon), there are a couple of instances when the lead male character Yuzaki Nasa is overwhelmed by something unexpected and adorable that his wife Tsukasa does or says. This is shown visually by Nasa taking a longer than usual pause before responding, but then instead of responding he suffers some reaction that causes him to cough violently, I think? The visual shows some white froth spraying from his mouth, but his back is turned to the camera, so I'm not entirely certain that it is a cough. Both times, Tsukasa is taken aback by his reaction and asks him in a concerned manner whether he is feeling alright.
These events are clearly played for a gag, but I think I'm missing some context behind them. I have seen anime nosebleeds, and their meaning has been discussed on this site before: Does the "bloody nose" trope necessarily imply a sexual situation?. This case does not seem to be a nosebleed, though. The anime has not shied away from depicting fountains of blood (for comedic purposes, of course) in Episode 1, so I'm sure they would have coloured the expulsion red if that was intended.
What exactly is happening to Nasa in these two instances?