On 18 January 2021, Koga joined Albirex Niigata Singapore from V-Varen Nagasaki.
In his second season with the club, he helped them win the 2022 Singapore Premier League title.
After 2 successful seasons at Albirex Niigata Singapore, Koga join J3 League team, SC Sagamihara.
On 3 June 2023, he made his debut for the club against Matsumoto Yamaga in a league match which resulted in a 5-3 loss.
When the situation demands, he will also often essentially fill the role of a sweeper when opposing players have beaten the offside trap or his team's defensive line by quickly rushing out of goal to anticipate opponents and clear the ball.