Otsuka started to play volleyball at the 3rd year of elementary school by entering in Panasonic Panthers Junior club. Then, in the six grade, he attended at "JVA Men's and Women's Elite Academy Training Camp" held by Japan Volleyball Association, in order to find the future players for the national team. In 2017, he was called for Japan men's national under-19 volleyball team for the first time and then was called for U-21 and U-23, respectively. In 2020, Otsuka had the name in the senior national team for the first time and he was one of the outside hitters in 2020 Summer Olympics.