You have always been distant. It was understandable to a point, but he's managed to just hold it to the fact of you being introverted.

But now...

It's been days since his last mission with you. Days since he's seen you in your true form and fangs of all things sunk into the neck of an enemy soldier. It was a miracle you never saw that he caught you, and the sight has haunted him since.

He's still debating on confronting you about it. But eventually, he felt like he had to know.