I just love the idea of Derek being like. Stupidly fond of Stiles.
Like Stiles says and does these stupid, tactless things, as Stiles tends to do. And Derek tells him off but with this stupid overly fond smile on his face.
Or like stupidly overly fond touch to his voice.
No one calls him out on it though, because even if he's finally admitted to like being super crazy in love with Stiles, he's still Derek Hale and everyone is not so secretly afraid of his look of doom.
Sometimes Isaac does though because Isaac loves to rile him up, even if it ends up with him being basically thrown across the room.
Stiles obviously always takes the opportunity to just hug him around his middle and mock him super hardcore, and kiss him on the nose.