Seto yells a lot. It's the hallmark of how he interacts with people.
Seto is angry a lot. He doesn't mince words.
All that said, though, I think he's probably the one character in all of YGO who's most devoted to the idea that things can get better. It's why he puts the past behind him, why he's focused so hard on the future. It's the future that can be made to improve.
It's the future that holds all the promise.
That's what he cares about.
.
The majority of Seto's battalion was comprised of monsters used to doing open battle on wide, flat plains. They were, in other words, ill-equipped to handle the maze-like, claustrophobic Domino City. They were escorted to Kaiba-Land under the custodianship of Roland Ackerman and his security team—with the pretense being that they were a new performance troupe who would hold "fake" tourneys at the park to the delight of the guests. Enough of these monsters resembled their likenesses on their respective Magic & Wizards cards that fans of the game wouldn't look twice at such a group.
Most people who didn't know the game probably wouldn't ask questions, either; Domino City was so strange as a matter of course. Seto was banking on this; he didn't want to think about the PR nightmare that would come out of his extradimensional bodyguards causing a scene in public.
Vorse Raider was as good as his oath; Seto only spotted him three times on the way to the park, and each of those times it was clear to the eldest Kaiba that his monster was specifically allowing himself to be seen.
"You are quite calm, my prince," Kisara said. "Mokuba has told me that you put up a front to prevent him from panicking in a dangerous situation. Are you doing this now, for me?"
Seto offered a soft, apologetic little smile. "I wish that I could say I was, Kisara," he said. "I think it would be much more . . . sentimental, if I could. But the truth is simpler: I am calm because I am confident. I know you worry, and I wouldn't want you to do anything else in this situation. Your family has been targeted, and it's only right for you to fear for them. But . . . I've faced multiple world-shattering events with far less than this to work with. Even if you, personally, don't remember any of those cluster-fucks," Seto gestured randomly, "the queen remembers, and I'm sure she could tell you. It wouldn't surprise me if she already has."
Kisara regarded Seto quietly for a time, then she nodded. "She has," she said. "You are correct."
Seto put a hand on his bodyguard's shoulder. "Trust in your strength. Trust in our strength. Everything will turn out all right."
Kisara nodded. "There is no force," she said, "from gods or devils, that can dethrone us."
"That's right."
"You know," Kisara went on, after a time, "there are those who claim you are a pessimist. I've seen it in articles. Nihilist. Doomsayer. A number of other such labels. I find this . . . confusing. I think you are, perhaps, the most violently optimistic man I've ever met."
Seto flashed a grin. "I get that a lot," he said. "I won't pretend I don't sensationalize when I'm in front of a camera. It's all part of the performance, after all. When I'm angry, in particular, I lean on hyperbole. By which I mean, of course, I crush hyperbole into a fine powder and snort it."
Kisara snorted laughter. "That's certainly one way to phrase it, my prince."
"But I do believe in a brighter future. I've put too much effort into all that I do, to not believe in a better tomorrow. Sure, sure, sunk cost fallacy. But, counterpoint, I'm better than others and I'm capable of doing what they can't."
"And you are so humble, too."
"Humility," Seto declared, eyes bright, "gets more people in trouble than pride does."
"I don't know if that's true, my prince."
"But you had to think about it, didn't you?"