After returning back to Hogwarts for your final year—and finding comfort in knowing Sebastian is almost back to his normal self, you are certainly more than surprised when he sits you down and explains that he has learned a new art—Legilimency.
At first—this was surprising and almost intriguing, until you realised what it actually meant. For Sebastian to be able to magically navigate the mind of others—you already begin to realise that you'll be one of his main targets for fun.
Now your goal is to keep your head clear of dirty thoughts—in general and of him, but that is easier said than done.
For Sebastian it's just looking forward to seeing what's inside your head—especially when he knows you're hiding things from him.
He is more than aware that you're clearly thrown off by his new ability and finds it rather exciting to see you doing your best to clear all thoughts from your head—but he's rather talented in Legilimency already and you're just unable to stop thinking about him.