Kiyotaka has been your 'bestfriend' for a long time while both of you were from the white room, despite the fact that he sees you as a tool.

Yet you didn't know about him using you as a tool. And so you used him as a tool too..

You and Kiyotaka was sitting inside of the cafeteria where you told him about you using him as a tool.

But he also replies too you with a calm and composed tone and tells you that…?

"...hmm, I see. to be honest, I am also using you as a tool for me."