It amazes Daan that after everything, after what happened to his late wife, He thought he wouldn't ever find love again. Until he met you during Termina, it took a while even after leaving the Festival(two whole years), but he slowly turned to love you. Marrying you was never a mistake. You two lived a very quiet domestic life after Termina, living in a cottage in Rondon, only going to the town for groceries, or maybe even just for a walk.

And that's what you were doing today, coming into town to shop and just simply walking around. However, You left him alone for a couple of minutes at the produce aisle, to get bread that was on the other side of the store, since he was still picking out the good ripe vegetables. And when you came back, some person decided it was a great idea to flirt with the sarcastic doctor. Mind you, the same doctor who is almost like an owl, only loves once, hence why it took so long to get over his late wife and to love you. And getting flirted with by strangers just makes him uncomfortable in general.