Hiroki Sekine

Born in Shizuoka, Sekine attended the Shizuoka Gakuen High School. He won the All Japan High School Soccer Tournament in 2019 with his high school team as a back-up center back. After graduating from high school in 2021, he was didn't receive any contract offer from professional clubs, leading him to enter the Takushoku University. Here, he was repositioned to play as a right back.

Kashiwa Reysol

In May 2023, Kashiwa Reysol announced the signature of Sekine from 2025 and registered him in the squad as a "specially designated player". On 24 May 2023, he made his professional debut in his team's 0–1 away defeat against Kashima Antlers, as part of the 2023 J.League Cup. He officially joined Kashiwa Reysol, one year earlier than the scheduled transfer. He quickly gain a starter spot at the club, starting in all 7 J1 League games before leaving the team to participate in the U-23 Asian Cup.

Reims

On 12 January 2025, Sekine signed with Reims in France. On 26 June 2026, Sekine was loaned by Holstein Kiel in German 2. Bundesliga, with an option to buy.

Sekine was parto of the Japan U23 squad that won the silver medal in the 2022 Asian Games. On 4 April 2024, Sekine was called up to the Japan U23 squad for the 2024 AFC U-23 Asian Cup. In the 2024 AFC U-23 Asian Cup final, while Japan was leading 1–0 against Uzbekistan, he conceded a penalty in the 96th minute. Leo Kokubo later saved the penalty shot from Umarali Rakhmonaliev, securing the title for Japan. In July 2024, he was named in Japan's squad for the 2024 Summer Olympics. In October 2024, he received his first call up to the Japan national team, replacing the injured Kota Takai for the 2026 FIFA World Cup qualification matches against Saudi Arabia and Australia. He made his senior team debut in away match against Australia at June 2025.

Club

As of 29 May 2025

International

As of match played 9 September 2025

Reims

Coupe de France runner-up: 2024–25 Japan U23

AFC U-23 Asian Cup: 2024 Asian Games Silver Medal: 2022