After he finished his high school career in Yokohama, Tazawa was not drafted by any of Nippon Professional Baseball's 12 teams, and joined the company team of Nippon Oil in the corporate league, unaffiliated with the NPB [REF].
In 2008, Tazawa posted a 10-1 record for Nippon Oil, with a 1.02 earned run average and 95 strikeouts in 88 innings [REF].