While he's glad that the pink-haired Arrancar is gone, Szayel has left Yumichika in a state of deep unsettlement. Whatever reaction he'd been expecting, it definitely hadn't been
this. Something more along the lines of shaking ruffled feathers and a huffy storming out, probably. Certainly not an uncomfortable amount of chuckling.
Definitely not leaving without getting in a last word - Szayel struck Yumichika as someone who always had to have things his way.
So when he turns around and finds that the door has been left open, he is immediately suspicious. He is also dying to see if there's anything more to Las Noches than this dreadful room, which puts him in a very interesting dilemma indeed.
He stares at the open door in silence, carefully considering his situation from every angle imaginable. Finally, he loses his patience and, fed up with his lack of activity, recklessly marches out of the room. Once through the doorway, his hesitation drains away, to be replaced with his customary arrogant boldness.
Maybe he'd just go find Aizen himself.
[Who will Yumichika encounter this time?! >w< ]