Tsuburaya competed at the 1964 Summer Olympics held in Tokyo, Japan, finishing sixth in the 10,000m event and lining up for the marathon as well, on the final day of competition.

Tsuburaya entered the stadium second, but was overtaken on the final lap by the furious sprint of Britain's Basil Heatley and finished third, earning the bronze medal.

Tsuburaya was mortified by the loss to Heatley, saying to fellow marathoner Kenji Kimihara, "I committed an inexcusable blunder in front of the Japanese people.

[3] Shortly after the Tokyo Olympics, Tsuburaya suffered from an ongoing back problem, known as lumbago.

On January 9, 1968, he committed suicide by slashing his wrist in his dormitory room where he had stayed during his training period for the Mexico City Olympics.

Tsuburaya had wanted to marry Eiko, but his military bosses refused to consent to a marriage until after the 1968 Olympic Games in Mexico City, and Eiko's parents had been unwilling to have her wait to marry until after the Games.

Yukio-kun, Hideo-kun, Mikio-kun, Toshiko-chan, Hideko-chan, Ryosuke-kun, Takahisa-kun, Miyoko-chan, Yukie-chan, Mitsue-chan, Akira-kun, Yoshiyuki-kun, Keiko-chan, Koei-kun, Yu-chan, Kii-chan, Shoji-kun: May you grow up to be fine people.