WULFRIC gulped. When he heard Aster's question, the first thing that flashed in his mind was his fan account - @astridsnumber1fan. This secret certainly had everything to do with Aster. But if he told the other about it, he couldn't imagine what he's reaction would be. Especially since the other was aware of his 'White Wolf' fan account.
Maybe this would be the last straw and Aster would really think of him as some kind of stalker. He could have passed it off and say that there was none, but his immediate reaction had already prevented him from using that excuse. If he said that now, with how perceptive Aster was, he would only think of him as suspicious.
As cold sweat continued to pour on his back, a certain information suddenly flashed in his mind, like a lightbulb turning on. It's not necessarily a secret, per se. More like something he hadn't mentioned to the other. But it was still important information that he should have told Aster long ago.