Omega!Prompto doesn't show up to school one day, and Alpha!Noctis is worried. He decides to go over to his house to check on him alone (everyone and their mother knows about Noctis'crush on Prompto and at the very least doesn't dissaprove), and finds out that Prompto began his first heat and the moment Noctis walks into the bedroom he's begging for Noct to knot him.
Noctis is very much unresistant to this idea.