The left-sided centre half moved to Liverpool's Academy from French side Orleans FC in November 2018. Koumetio was originally on the books of his hometown club Olympique Lyonnais. The French U17 international defender had only been a year at the club before he was handed a seat on the bench versus Arsenal in the Carabao Cup on 30 October 2019. On 9 December 2020 he made his full debut, coming on as a second half substitute in Liverpool's Champions League group stage game against Midtjylland in Denmark. 

Koumetio was loaned to Austria Vienna for 2022/23 but he was recalled in January after dropping to their reserve side. On his return to Under 21 action, he scored an outrageous goal from inside his own half against Paris St Germain in the Premier League International Cup. He was a regular at centre back for the remainder of the Premier League 2 season. Seemingly out of the first team picture, he was loaned to French Ligue 2 side USL Dunkerque for 2023/24. After just nine appearances Koumetio was recalled in the January transfer window and loaned to Blackburn for the remainder of the season. His sole appearance there was as a substitute in an FA Cup tie with Newcastle. He was an unused substitute twelve times in the Championship and played one full game in Premier League 2. The arrival of Arne Slot as manage that summer was a fresh opportunity to impress but his departure appeared imminent within a few weeks when he was moved to the Under 21 training group. On 9 August Koumetio agreed a two year deal with Scottish premiership side Dundee. He made a total of 20 appearances for Dundee in the 2024/25 as they avoided relegation from the Premiership,