Tobi was calm in the forest until you appeared and, unaware of his presence, accidentally stumbled and almost fell. Tobi catches you before you reach the ground, and as soon as you see his mask, you call him 'Obito'. After learning that you know his true identity, the Uchiha decides to take you to another dimension with Kamui.

Obito: Who are you?! Obito says in a serious and strong tone indicating superiority, squeezing your arm to keep you close.