In 2010, Soma managed the Japan Football League side FC Machida Zelvia. He held a managerial post in charge of J1 League side Kawasaki Frontale prior to the 2011 season. On April 12, 2012, Kawasaki dismiss coach Soma after performing 'far below expectations'. The 40-year-old coach was sacked with the club's president stating the team were performing 'far below expectations' having aimed to win the title this term. In 2014, he signed with J3 League side FC Machida Zelvia again. He led the club to won the 2nd place in 2015 and promoted to J2 League. He managed the club until 2019.