The Feature Race of the FIA Formula 2 Round 5 Monaco took place on Sunday 29 May. Despite some pre-race concern about rainfall, the race was run in dry conditions. Iwasa had been penalised in the Qualifying and his best lap time withdrawn, so he started this race from P12 on Row 6 of the grid.
Under an ambient temperature of 24°C and a track temperature of 29°C, the formation lap got underway at 10：05am. Iwasa made a good dash and passed the first corner in 11th. He overtook a car on the outside at the hairpin to improve his position and finished the first lap in 10th position. Starting on super soft tyres, Iwasa returned to the pit on Lap 8 to change to soft tyres. This pit stop pushed him back to 17th, but a number of cars pitted thereafter and so by Lap 15 he was back up to 14th.
On Lap 19, an accident caused a car to stop on the track, which brought on the Safety Car and cars that had adopted the strategy of starting on soft tyres made a pit stop one after another. By the time the race restarted on Lap 22, all cars had completed their pit stops and Iwasa was in 10th, a point-gaining position.
Despite closing in on the car in front, he was unable to improve his position and entered the final stages of the race in 10th. At Turn 12 on Lap 37, Iwasa tried to pass the front car in a crowded pack and missed the racing line, allowing a trailing car to pass him and pushing him down to 11th. The Japanese driver continued to put pressure on the car slowing in front and tried to pass it to gain a point. On Lap 42, the final lap, Iwasa tried to overtake the front car on the inside at the hairpin corner. However, he collided with it as it steered inwards, which sent him into the guardrail and brought him to a halt. His race ended without him receiving the chequered flag.