A cheerful teen whose personality is bright like the sun above, Tidus possesses the heart of an ace athlete. His main goal is to defeat his father, whom he detests to no end.
A light-hearted, cheerful youth able to calm others even through the most trying situations.— Dissidia Final Fantasy description
Tidus is an ace blitzballer who travels 1,000 years into the future, due to a cataclysmic event. He awakens to find himself in a futuristic and destroyed, version of his home city of Zanarkand. A creature known as Sin demolished his hometown years ago, and still ravages Spira.
The only want to placate Sin is through Pilgrimages, in which a summoner performs a sending ritual. He joins a summoner named Yuna, but throughout his journey learns the truth of this ritual. As he takes action to put a stop to it, he learns the truth of his origins. Tidus is a dream of the Fayth, an illusory copy of Zankarkand.
During the 12th cycle, Tidus aligns himself with Chaos. Here, he has a much different demeanor than in Final Fantasy X. As opposed to being cheerful and optimistic, he appears arrogant and aggressive. Is this the same Tidus? In a sense, this person is actually more so Shinryu. Some theories exist that Shinryu is the person the Fayth based Tidus on. Perhaps the person who we think is Tidus is actually Shinryu. Why else is Tidus so rude? And why doesn’t he remember Yuna?
Yuna: “Hey… It’s me, Yuna. The summoner, remember?”
Tidus: “I don’t know any Yunas. Now get outta my way! This’s my fight. It’s got nothing to do with you!”
It’s a mystery, but it’s most likely due to him forgetting his memories. Yuna attempts to remind him of the adventures they shared:
Yuna: “Yes it does! It has a lot to do with me. You…remember our journey together, don’t you? Even I don’t remember everything. But… I do remember you. I’d never forget you.”
Tidus: “I don’t–“
Yuna: “You fought, to keep me safe. You told me all kinds of stories.”
Tidus: “I don’t know what you’re talking about, okay? I told you–get outta my way! Don’t make me go through you!”
Yuna: “I’m not moving. I know you won’t hurt me.”
Tidus: “What are you talking about?”
Yuna: “Tidus… I…I’ve wanted to see you for so long.”
Yuna: “If you just remember, there won’t have to be any more fighting. I’ll stay with you, and keep you safe until you do. So please…come with us.”
Tidus: “Look, I–“
However, even in the 12th cycle, this is mostly likely Tidus. It only begs the question as for why he’s so prickly. He’s not all bad, but perhaps it’s due to the hate he has for his father:
Jecht: “You… What’re you doin’ in a place like this?”
Tidus: “Taking you down, old man. What else would I be doin’ here?”
Jecht: “Heh. Is that it? They call you here to try and beat me, did they? You just can’t get enough of followin’ in my footsteps, can ya, boy!?”
Tidus: “Can the talk, already. Bring it on. Or are you too scared?”
Jecht: “Stupid kid… Gone and gotten yourself brainwashed. Well, you asked for it, ya good-fer-nothin’ punk!”
So when did Cosmos call Tidus to the 13th cycle of World B? Most likely Tidus finds out that Jecht is Sin, but definitely before either fades to the Farplane. Tidus still hates his father for all of the emotional torment endured:
Tidus: “Oh, come on… You’re fading already?”
Jecht: “Looks like it.”
Tidus: “I hate you. I hated you so much… I’ve always wished you’d be gone. But deep down… what I really wanted was just… your approval… for you to… tell me that I’ve grown strong–“
Jecht: [Ahh.] “Looks like the kid will never grow up.”
Tidus: “That’s not my fault. I can’t help it. I’m your son, after all.”
Jecht: [Haha.] “I guess you are. Hey, cry-baby…You’ve grown strong.”
In the end, they reconcile. But this is the practice trial. They’ll have to do it again once they make it back to Spira.