From childhood, Soeno was very interested in martial arts, and learned Judo. Originally he found that Karate was not strong compared to Judo, but Karate was evolving and becoming much stronger. He first studied Wado-ryu a while. He began the study of Kyokushin karate at the headquarters of Kyokushin Kaikan at Ikebukuro, Tokyo, where founder Masutatsu Ōyama taught on September 1, 1964. Soeno practiced with the senior pupils who were Shigeru Ōyama, Yasuhiko Ōyama, Tadashi Nakamura and Hideyuki Ashihara at the time. After entering Josai University, Soeno founded the Karate club and taught karate. Miyuki Miura was 2 years one's junior at the club. Soeno had reached the rank of shodan on April 15, 1967. Televised kickboxing was a huge boom from 1965 to 1975 when it was broadcast on the four TV stations, TBS, Nippon Television, TV Asahi and TV Tokyo all over Japan. TV Asahi requested a player from Kyokushin in February, 1969, and Masutatsu Ōyama elected Soeno and Terutomo Yamazaki to enter the competitions. Ōyama also founded a kickboxing gym called Kyokushin Gym where they practiced kickboxing about two months before entering the kickboxing competitions in April, 1969. Soeno fought in the welterweight division at kickboxing. Kyokushin was planning to hold the First All-Japan Full Contact Karate Championships at the Tokyo Metropolitan Gymnasiumin September, 1969. It was not only a karate championship, but martial artists of various kinds also participated in this competition. Athletes included Gidon Gaddary who was an Israeli Judo player weighing over 100 kilograms; Paul Jackson who was a heavyweight boxer from the United States; and three Muay Thaiboxers from Lumpinee-ranked boxers including Birahon, Sakao and Samanso. The competition was fighting against other combative arts. The rules were simple: It was a foul to use a hand or elbow to the face and to attack a man's vital point. The players did not use any protection. They fought using bare hands, bare knees and bare legs. Soeno lost Yamazaki at finals and won 2nd place. After graduating University, he opened ‘Soeno Dojo’ and ‘Soeno Gym’, giving lessons in both karate and kick-boxing. He also practiced Muay Thai in Bangkok, and Karate in the United States. He founded The World Karatedo Association Shidokan and The Japan Fighting Association New Fighting Shidokan in 1981.
