Sporting director Sebastian Kehl revealed that Dortmund had been monitoring Lerma for years, maintaining close contact with his family to secure the deal.
"We've been monitoring Justin for some time and have maintained close contact with the player and his family ever since," said Kehl.
Bild reports that Dortmund staff made multiple trips to Ecuador to ensure the player felt integrated even before his arrival. Head coach Niko Kovac is expected to include Lerma in first-team training next summer, giving him time to adapt before making his Bundesliga debut. Lerma has already visited the Dortmund facilities on several occasions, too, and has been impressed by the atmosphere.