Soma was born in
Shizuoka on July 19, 1971. After graduating from
Waseda University, he joined
Kashima Antlers in 1994. He played as left-back and became one of the main player in a successful era of the club. In the 1990s, the club won several titles: the
1996 J.League,
1998 J.League,
1997 J.League Cup and
1997 Emperor's Cup. He was also selected for the Best Eleven for four years in a row (
1995-
1998). In 2000, the club won all three major titles in Japan:
J1 League,
J.League Cup and
Emperor's Cup. However at Emperor's Cup in December 2000, he sustained an injury and he could not play for about a year. Although he came back in the latter half of 2001, his opportunity to play decreased behind
Augusto. In 2002, he moved to
Tokyo Verdy on loan. He returned to Kashima Antlers in 2003 and moved to
Kawasaki Frontale in 2004. At Kawasaki Frontale, he played as defensive midfielder and sweeper. He retired at the end of the 2005 season. ==International career==