Yuki Kobayashi has signed a contract with Jagiellonia Białystok, which is valid until June 30, 2028, with an option to extend for an additional twelve months. He transferred on a permanent basis from the Portuguese club Portimonense. Kobayashi expressed his excitement about joining the ambitious club and his eagerness to adapt and succeed with them. The 24-year-old Japanese player primarily plays as a central defender and is known for his dominant left foot. He joined Portimonense after his stint with Celtic, where he played only seven matches. Last season, he participated in 25 games in Portugal's second division. Kobayashi is the sixth signing for Jagiellonia in the current transfer window.