He made his K-1 debut on December 2, 2006, at the K-1 WGP 2006 Final undercard, against Mitsugu Noda, winning the fight by split decision.

[2] On his next fight in Yokohama he stunned the K-1 world by a convincing victory over French kickboxing legend Jerome Le Banner.

[2] After three consecutive wins at Yokohama, Hawaii and Amsterdam Sawayashiki earned himself a wildcard entry to the K-1 Final Elimination against the K-1 Asia winner Yusuke Fujimoto.

He suffered his first K-1 loss by first round Knockout after taking a tremendous right punch to the face.

Sawayashiki's career went downhill from there, losing 4 more straight fights in a row, 3 KO losses to Musashi, Cătălin Moroșanu and Glaube Feitosa plus a punishing three round fight against Jerome Lebanner in the 2008 Final 16.