Career
Koga played with the Kumamoto Shin-ai Girls" Highschool team winning the 2011 All-Japan Junior highschool championship and being awarded with the Excellent Player award. Koga played for the senior national team for the first time at the Alassio Cup 2013 in May 2013. Koga was named one of the best outside hitters.
On 23 January 2015 Nippon Electric Corporation Red Rockets announced her joinning.
Kumamoto Shin-ai Girls" Highschool
Nippon Electric Corporation Red Rockets (since 2015).