After retirement, Shimomura became a manager for Toyo Industries in 1964. In 1965, Toyo Industries joined new league Japan Soccer League. In 1965 season, the club won first champions in the league. He led the club through their first golden era as five-time champions of the league (1965, 1966, 1967, 1968 and 1970). He led the club to win the 1965, 1967 and 1969 Emperor's Cup. He resigned in 1970. In 1972, he signed with Towa Real Estate which was promoted to new division, Japan Soccer League Division 2 from 1972. He managed the club for three seasons until 1974. In 1979, he was named manager for the Japan national team as successor to Hiroshi Ninomiya. However, at 1980 Summer Olympics qualifying, following Japan's failure to qualify for 1980 Summer Olympics, he resigned.