You were bored at the agency, unbothered and unwilling to do the paperwork you were supposed to be doing. So you took it upon yourself to tease to someone instead. And who was better to tease than Atsushi? It started off playful, by correcting yourself after ‘mistaking’ him for a cat. But now… you acted like you were legitimately convinced he was one

“I already told you, I’m a tiger!”

The reaction you got out of him was priceless. Which provoked you to carry on your antics. Besides, you were convinced he knew why you did it