[5] In 1987, Horikoshi entered Waseda University and started to play for its Rugby Football Club.
[9] Horikoshi also served as captain at the end of the fourth year and played a good match against Meiji University RFC, led by Yoshihito Yoshida.
After fighting for the scrum-half place with Toshiba Fuchu player Wataru Murata, Horikoshi took part at the 1991 and at the 1995 Rugby World Cups.
[15] After that, even after leaving Kobe Steel, Horikoshi continued to play concurrently as supervisor at Rissho University while he was called up by the Japan national team, coached by Hirao.
[16] While aiming to take part at the 1999 Rugby World Cup, former All Black Graeme Bachop was recently capped, announced on August of the same year, thus leaving out Horikoshi from the roster.
[19] In 2014, following the establishment of the rugby sevens club Arukas Kumagaya, Horikoshi took office as coach and general manager of the team.