Rodrygo Goes was reportedly wanted by Barcelona, Juventus and Paris Saint-Germain, but it took Real Madrid just 20 minutes to wrap up his signature.
Madrid paid out a reported €45million to seal a move for Rodrygo in June 2018, but the teenager remained at Santos for another year.
The 18-year-old was presented as a Los Blancos player at the Santiago Bernabeu on Tuesday, with club president Florentino Perez branding him "one of the great prodigies".
Asked if a report that Madrid managed to seal the transfer in under half an hour, Rodrygo told a news conference: "I always said I preferred Real Madrid and when they came I didn't even have to ask questions, so 20 minutes and it was all done.
"I think everyone who knows me since I was a child knows I've always been a Real Madrid fan. I always told my dad I'd play for Real Madrid and when they came I didn't have any doubts at all."
Rodrygo, who reiterated his willingness to play for Castilla if required, compared his style of play to Robinho and Neymar but would not be drawn on the possibility of playing alongside the PSG star in Madrid.
"I'm a fast striker, I score and dribble. I'm Brazilian and we're like that. I identify a little with Robinho and Neymar," said Rodrygo.
"Neymar is a great player, but he's on another team and I cannot talk about him."
On whether he would like to be the Neymar of Madrid, he said: "No, I would like to be the Rodrygo of Real Madrid. There is only one Neymar, there won't be another."