Koga, the 100-meter backstroke world champion, placed second in the 50 backstroke final with a time of 22.98 seconds, 0.29 off the previous mark he set in Wednesday's heats. American Peter Marshall broke the world short-course record to win the race in 22.73.
Tamura finished in sixth in the women's 50 breaststroke final, cutting 0.05 off the national record of 30.69 she set earlier in the heats.