In the championship finale at Le Castellet he retired from the first two races but ended his maiden Formula 4 full-time season with a third place finish.

Imola would be the highest point in the series for him, as Slater would dominate the championship, leaving Yamakoshi to settle for podiums instead of fighting for wins.

At the third round in Vallelunga Circuit, he came third in all three races, and enjoyed consistent success throughout his campaign, but would become less consistent in the latter half of the season, and scored no points at the final round at Monza, getting narrowly beaten by teammate Jack Beeton for series runner-up by two points.

Yamakoshi finished the championship in 3rd place with two wins, three pole positions, three fastest laps, seven podiums and 220 points.

Yamakoshi competed in the Formula Regional Middle East Championship at the beginning of 2025, racing with Pinnacle Motorsport.

[7] In 2025, Yamakoshi moved up to the Formula Regional European Championship, continuing with Van Amersfoort Racing.