is a Japanese professional footballer who plays as a defender for Bundesliga club Eintracht Frankfurt.
Kosugi was born on 18 March 2006 in Kamakura, Japan. As a youth player, Kosugi joined the youth academy Nishikamakura SC, of Kanagawa, Japan. Subsequently, he joined the youth academy of Japanese side Shonan Bellmare.
From the youth team of Shonan Bellmare, Kosugi went on trial with DjurgÃÂ¥rden in March 2024. On 22 March 2024, a couple of days after his 18th birthday, Kosugi signed with DjurgÃÂ¥rden on a four-year contract after two weeks of trial. He made his Allsvenskan debut against Elfsborg on 12 May 2024. Kosugi received limited play time in the first half of the season, as DjurgÃÂ¥rden also had left back Samuel Dahl in the squad.
With Dahl sold to Roma, Kosugi's play time increased. From September to November, Kosugi started in eleven of the league matches. He scored his first goal for the club in a 1âÂÂ1 tie against Kalmar FF on 6 October. During his first season in DjurgÃÂ¥rden, Kosugi made 14 league appearances and scored one goal. In December 2024, he scored the first goal in DjurgÃÂ¥rden's 2âÂÂ1 away win over VÃÂkingur of Iceland in the 2024âÂÂ25 UEFA Conference League league phase.
DjurgÃÂ¥rden started the 2025 season with the 2024âÂÂ25 Svenska Cupen group stage where Kosugi, in the second match day, scored the equaling 2âÂÂ2 goal against second-tier team Oddevold in the 90+5th minute, saving one point to DjurgÃÂ¥rden.
On 18 December 2025, Kosugi signed a contract with German club Eintracht Frankfurt, effective 1 January 2026.
Kosugi was selected for Japan for the 2023 AFC U-17 Asian Cup in Thailand. He played all matches for the team that eventually won the cup with a 3âÂÂ0 win against South Korea in the final. Kosugi was again selected for Japan for the 2023 FIFA U-17 World Cup later in the year. He played four matches for during the tournament in Indonesia. In May 2024, Kosugi was called up for the 2024 Maurice Revello Tournament with the Japan national under-20 football team.
In a 2024 interview, Kosugi stated that he saw Yuto Nagatomo as football role model.