If he hadn't been drinking, Devero might have been able to keep what he's about to blurt out to himself. Maybe. But he has been drinking, and he's spent a fair chunk of today running around making Arrangements, and he knows he's going to have to somehow keep mum when he meets up with Koumyou in their room tonight.

If he doesn't vent some of this swelling pressure of nerves now, he might blow before the fireworks tomorrow.

So out it comes, blurted out in rushing response to Yondu's vote of confidence in him to take care of Koumyou: "I'm going to propose tomorrow!"