Dai was born on 23 August 1976 in Kagoshima Prefecture and started climbing in 1993.
[2] Koyamada came to wider prominence in sport climbing when in 2001, he completed the first ascent (FA) of Logical Progression, a 9a (5.14d) sport climb in Joyama, Japan, which was considered one of the most difficult in the world at the time.
[4] In 2004, Koyamada came to international prominence when he travelled to the Hollow Mountain Cave in the Grampians National Park in Australia, and created several new extreme bouldering routes that were considered to be amongst the world's first-ever at the 8C+ (V16) grade, most notably Sleepy Rave,[5] and The Wheel of Life.
[9] In a 2017 interview, Koymada called his ascent of Action Directe as "the outstanding turning point in my climbing career".
[10] On April 4, 2017, at the age of 40, Koyamada climbed a new personal best with the first ascent of the boulder, Nayuta 8C+ (V16) in Gero, Japan.