Tomozuna stable
Koga did karate for two years in elementary school, and judo in his second year of junior high school. He had not shown much interest in sumo but was asked by his parents to take part in sumo competitions. It was at one such competition in Fukuoka that he was spotted by the wrestler Kaiki, later Tomozuna Oyakata. After being introduced to Kaiki by a mutual acquaintance in Nōgata, the young Koga was recruited to Tomozuna stable upon graduation from junior high. Kaiki thought so highly of the apprentice that he promised Koga's parents that he would become a "sekitori" by the age of 20. However, because the move had been set up by others around him, and he had not ever had the ambition to be a "rikishi" himself, Koga initially had doubts that he would be able to succeed in sumo.