Borussia Dortmund have signed Reinier from Real Madrid on a two-year loan.
Reinier, 18, joined Madrid from Flamengo for a reported €30million in January and played for the Castilla side in the Segunda B1.
He made just three appearances under Raul before the season was put on hold amid the coronavirus pandemic.
The Brazilian will spend the next two campaigns in the Bundesliga with Dortmund, who have built a reputation for developing young talents by providing first-team opportunities.
Reinier said: “I am happy to be with BVB now. The club is known for betting on young players and making them better.
“I want to learn a lot here, play a lot and help the team to be successful. I hope that we will have many happy moments together.”
Reinier, who won the Campeonato Brasileiro and Copa Libertadores with Flamengo in 2019, had been training with Zinedine Zidane’s team.
“Reinier is a player who brings enormous talent and can be used in various attacking positions,” said Dortmund sporting director Michael Zorc.
“We have been watching the boy for more than two years. He has great technical skills as well as good physical strength.
“After a long break from competition we will give him the time he needs to get used to German professional football. He will then be an additional option in attack.”
Achraf Hakimi spent two years on loan at Dortmund from Madrid but opted to join Inter for a reported initial fee of €40m when his spell at Signal Iduna Park ended.