This scene is even more magnificent if you look at the individual frames. He actually takes the pen out with the checkbook and tosses it into his other hand and spins it around without even looking at what he’s doing. You can see the pen go flying through the air in the gif too but I somehow never even noticed this before until just now. You are such a show off, Kaiba. XD
The man has aim, but I’m willing to bet he got that good from the military training under Gozaburo. Remember, he can lodge a card into the skin with a good throw & most can’t do that. The man has a sharpshooter’s aim & that’s scary as hell, but him doing this without looking? It’s those little things he does that makes him cool & Mokuba never gets tired of it. Part of him does it to show off, the other does it cuz Mokuba is left in awe every time & it makes him happy.