"Leon? What the heck?" Aaron thought that the appearance of his father is enough to surprise him for one day, but after seeing Leon and his uncle Leo together, he doesn't know what to say. Everything that is happening today is coming at him so unexpectedly.
"Hey, buddy! I know I have a lot of explaining to do, but for now, we have to leave this place quickly." Since Aaron is Arion's son, Leon is somewhat afraid of Aaron's temper. He can tell just by looking at Aaron's face that he is angry and has a lot of questions from him.
For him to not face Aaron's angry self right away, Leon decided to make an excuse that they should leave the place right away. His reasoning has a point, but anyone can tell that he is only making excuses.
"Don't buddy me. Don't think that I won't be interrogating you after this." Leon is one of those people who he trusted the most, and yet, Leon hid the truth from him and his sister about Arion.