The defensive midfielder becomes Hull's fourth signing of the summer following the arrivals of Matt Targett and Oscar Zambrano, and had also attracted interest from fellow Premier League new boys Ipswich Town and been linked with a move to Leeds United before opting for the Tigers.
Morita leaves Sporting CP after four trophy-laden years in Lisbon, during which he won back-to-back Primeira Liga titles and the Taca de Portugal, scoring 11 goals and adding 16 assists in 166 appearances, and helped the club reach the Champions League quarter-finals last season, making 23 appearances in Europe's premier club competition alongside 11 in the Europa League.
Born in Takatsuki, Morita made his professional debut for Kawasaki Frontale in February 2018 and won the first of two J1 League titles in his debut season, later adding the J. League Cup and Japanese Super Cup in 2019 and a domestic double of the Emperor's Cup and J1 League in 2020, a campaign that also earned him a place in the J. League's Best XI.
After 108 appearances for Kawasaki, he moved to Portugal with Santa Clara in January 2021, making 59 appearances over an 18-month spell before his switch to Sporting in 2022.
Internationally, Morita has earned 40 caps for Japan since making his debut in 2018, featuring three times at the 2022 World Cup and scoring one of his six international goals in the quarter-finals of the 2024 AFC Asian Cup, though he was not part of Japan's squad at this summer's tournament.
His arrival gives Hull significant experience in central midfield as the club prepare for their return to the Premier League, adding to a summer of recruitment that has also brought in goalkeeper Konstantinos Tzolakis from Olympiacos, with the club continuing to pursue further additions including Aston Villa midfielder Leon Bailey as it builds a squad capable of competing in the top flight.