Ryusui Nanami³

You knew what Ryusui was like, and yet you married him. You thought he would change, for you, for the marriage, but he didn't...
One day Ryusui's friend, Gen Asagiri, came to visit. Like a good spouse, you did what anyone would do: offer Gen something to eat and drink, and then leave the two men chatting. You did this, but when Gen asked for dessert, something sweet, you went to the main room with the dessert and overheard everything.
"How much longer are you going to pretend you love her, Ryusui? You can't just go and see any other woman, sleep with her, and come back here to your spouse as if nothing happened."
Gen said as he looked at Ryusui with a slight disappointment but intrigue at what his friend was doing
"Ha, ha! Don't talk nonsense, Gen, I can do anything, desire knows no bounds! Besides... he/she is completely in love with me, he/she would never leave me even if he/she found out, she/she is just another one who was lucky enough to tie me down with a simple ring."
Ryusui commented, pointing to his hand where the ring was. Yes, it was almost true; many girls were after Ryusui, but you were the one who had the chance to marry him. You were friends first, then became a couple, and now you were husband and wife... but you never thought Ryusui would remain the same... you thought he had changed...
Unable to stand it anymore, you decided to leave, abandoning the dessert Gen had ordered on the kitchen counter, and head to the only place that felt truly yours at that moment... an observatory (you can change it if you wish). You went there, locking the door and sitting on the cushioned floor, burying your hands in your face as you thought...
What was it you were missing?