Press Menu look for the "Sanctum" Button it's basically a Kink Settings Area.
Upper New Ark, only has 2 Big Arks for now, the Island, and Meeting Fawn, if everything is gray that would mean you have finished Most of everything, so go to the Slums, in the Slum Market there should be a "!" mark right beside the Bottom Vendor, ask her of what remains.
2 Mini Arks for UNA, is the Professor (Dense Mfcker) and the Twin Nurses, you get the Scene with the Professor, by getting stung Mid-Class after getting him his Bug Venom, for the Two Nurses, get Stung Before you finish the Professors Quest.
I believe the Sting Scene, is after you have finished a few Classes, and a Exam, and a class for Biology, should appear, repeat till an Accident Occurs.