Born in Tokyo, Terachi began competing professionally in 1998 and reached a career high singles ranking of 219 in the world, winning 17 ITF Futures titles.

His best performance on the ATP Tour came at the 2001 Shanghai Open, where he won his way through to the quarter-finals, with wins over Cecil Mamiit and Michael Tebbutt.

He made the Japan Open second round twice from six appearances, including 2005 when he defeated Philipp Kohlschreiber.

[2] In addition to the Davis Cup he also represented Japan in the Asian Games and won a doubles bronze in Bangkok in 1998, partnering Michihisa Onoda.

He was a gold medalist in the team event at the 2002 Asian Games in Busan, with his upset win over South Korean's Lee Hyung-taik giving Japan an unassailable 2–0 lead in the final.