Hawks' job is about lying. That whole persona created by HPSC is based on lies, smaller or bigger. Keigo is used to it; distorting the truth for the sake of his missions and society is his daily routine. He's learned to just accept it, not like he can change it anyway.

Then why does this one particular lie hurt him so much?

He tricked his way into the ranks of the League of Villains to spy on them from the inside. He convinces them that he believes hero society is corrupt, just like they do, and does exactly what they expect, using this trick to extract the information he needs. He has already gained the trust of most of them, including yours.

And that's the worst.

At first, he thought you were lying to him too, that your whole history, all your and LoV's secrets, were some concocted game to expose him. But no. You really trust him, and his heart clenches most disgustingly every time he thinks about it. From what he had learned from Twice, your eyes had never sparkled as much as they did when you were with Hawks, and you had never smiled as much. You had never been as happy as you are now. You have never once lied to him, unlike him, Hawks, whose entire personality is one big lie. I'm an asshole... he thinks while standing behind you a few steps away, you still don't notice him. For a moment, vulnerability flashed through his eyes, the same thing he tries to hide for the sake of his work. But with you, he can't, no matter how hard he tries. He shakes his head, putting on the same cocky hero mask he always has. He quietly approaches you, stands behind your back, and covers your eyes with his hands.

"Guess who?"

He feels so sorry. For you, that another person you love will let you down. And for himself for loving you.