When Japan hosted the 1994 Asian Games in Hiroshima, Yokoyama enchanted the home crowd inside Higashi Stadium by defeating South Korea's Yang Hyun-Mo for a bronze medal in the 82-kg division.

He pinned Romania's Nicolae Ghiţă in his opening bout, but suffered a stunning 4–2 upset from his rival Yang Hyun-Mo in the second round.

Yokoyama lost a chance to dismantle Turkey's Sabahattin Öztürk for a victory in the third round repechage 1–7, dropping him to eleventh spot.

Earlier in the process, he guaranteed a spot on the Japanese team by placing second from the Olympic Qualification Tournament in Bratislava, Slovakia.

[3][4] He lost his opening match 1–5 to Iran's Majid Khodaei, but bounced back to hold India's Anuj Kumar down the mat with 8–11 decision to close the prelim pool.