He played as a centre and was known for his powerful running and tackling. He played for Meiji University and for Kobe Steel Kobelco Steelers in the Japanese Top League. Motoki had 79 caps representing Japan, scoring 9 tries, 45 points in aggregate, from 1991 to 2005.
He was selected for four Rugby World Cup finals, in 1991, without playing, in 1995, playing in three matches, 1999, again in three matches, and 2003.
He never scored in any of his World Cup presences.