FC Tokyo captain Kuryu Matsuki has joined Southampton on a four-year deal, the English Premier League club announced Tuesday, with the 21-year-old set to spend the upcoming season on loan at Goztepe in Turkey. The left-footed, box-to-box midfielder joined FC Tokyo in 2022 out of Aomori Yamada High School and earned a starting spot in his first year. He made 71 J-League appearances and scored five goals in two-and-a-half seasons. “I want to build on the range of experiences I have had at FC Tokyo and keep taking on challenges in the way I am accustomed to doing,” the Hokkaido native said on the…