Naasei joins the Spanish giants in a deal reported to be worth around €2 million and will initially start with Real Madrid Castilla, the club's reserve side.
The reserve side competes in Spain's third tier, providing the Ghanaian with an opportunity to adapt to another level of competition while remaining within Real Madrid's first-team structure.
The versatile defender has agreed a two-year contract, with the possibility of extending it to five years if he progresses into the first team.
The move comes just three years after Naasei left Ghana to begin his European adventure.
He began his football education with Emmanuel City Football Academy before making the move to Spain in 2023.
Granada brought him into their youth system, where he quickly caught the attention of the club's coaches. His progress was rapid enough for him to move into the club's reserve setup and eventually the first-team environment.
Granada confirmed in 2024 that Naasei had renewed his contract after his impressive progression through the academy.
He made his senior Granada debut later that year, starting against Levante in LaLiga Hypermotion.
The defender had attracted attention from clubs outside Spain, but Madrid moved decisively to secure his services.
Naasei's primary position is centre-back, but his versatility is another feature that has helped his development.
The 1.85m defender is right-footed and can also operate at right-back, giving coaches an additional option when building their defensive structure.
Naasei made his debut for Ghana featuring in the friendly against Mexico in May and was part of the provisional squad for the 2026 World Cup.