Born and raised in Shizuoka, Sasaki was a talented wrestler and also began training in Brazilian jiu-jitsu from a young age. He wrestled for three seasons at Hiryu High School, finishing in the top 16 at the All-Japan High School Greco-Roman Wrestling Championships, and in 2009 Sasaki won the All-Japan Combat Wrestling Open Championships for the under 66 kg division. That same year, he also finished second at the All-Japan Amateur Shooto Championships. Later in 2013, Sasaki won the ADCC Japan Trial for the under 66 kg division.
Sasaki started his professional career in 2010. He fought mainly for Shooto, but also fought for DEEP and GCM early in his career. Sasaki faced Yo Saito on December 18, 2010, at Shooto: The Rookie Tournament 2010 Final. He defeated Saito via unanimous decision after two rounds and became the 2010 Shooto 143-pound rookie champion. Sasaki faced Tetsu Suzuki on January 20, 2013, at Shooto: 1st Round 2013 for the Shooto Pacific Rim 132-pound title. He won via unanimous decision and became the new champion. Sasaki defended his title on July 27, 2013, at Shooto: 3rd Round 2013 against Kenji Yamamoto. He won via knockout at 11 seconds in the first round and retained the title. Shortly after the bout, Sasaki relinquished his title in order to be able to fight for Shooto's world title. Sasaki faced current ZST 132 lb champion Keisuke Fujiwara on January 13, 2014, at Shooto: 1st Round 2014. He won via submission due to a rear-naked choke in the first round.
Ultimate Fighting Championship
In July 2014, it was announced that Sasaki had signed with the UFC. He made his debut against Roland Delorme at UFC Fight Night 48 on August 23, 2014. Sasaki won via submission in the first round. The win also earned Sasaki his first Performance of the Night bonus award. Sasaki faced Leandro Issa on December 20, 2014, at UFC Fight Night 58. He lost the fight by submission in the second round. Sasaki faced Taylor Lapilus on June 20, 2015, at UFC Fight Night 69. He lost the fight via TKO in the second round. Sasaki faced Willie GatesMay 8, 2016, at UFC Fight Night 87. He won the fight via submission in the second round. Sasaki was expected to face Matheus Nicolau on November 19, 2016, at UFC Fight Night 100. However, on November 3, Nicolau was pulled from the bout after USADA revealed a potential anti-doping violation from a sample taken October 13. Sasaki next faced Wilson Reis on February 11, 2017, at UFC 208. He lost the fight by unanimous decision. Sasaki faced Justin Scoggins on June 17, 2017 at. Sasaki suffered almost two rounds of damage but managed to sink his arm around Scoggins' neck and submitted him via a rear-naked choke in the second round to win the fight. This fight won Sasaki his second Performance of the Night bonus award. Sasaki faced Jussier Formiga on September 23, 2017 at. He lost the fight via submission in the first round. Sasaki was scheduled to face Magomed Bibulatov on April 21, 2018 at UFC Fight Night 128. However, Bibulatov was removed from the card due to back injury, and the bout was cancelled. Sasaki faced Jenel Lausa on June 23, 2018 at UFC Fight Night 132. He won the fight in round two via a rear-naked choke submission. Sasaki faced Alexandre Pantoja on November 17, 2018 at UFC Fight Night 140. He lost the fight via rear-naked choke submission in the first round.
Rizin FF
Sasaki faced Manel Kape in a 130lbs catchweight bout at Rizin 14 on December 31, 2018. He won the fight by unanimous decision.
Championships and accomplishments
Mixed martial arts
Shooto
*Shooto Pacific Rim 132 lb title
*One successful title defense
*Shooto rookie 143 lb champion
Ultimate Fighting Championship
*Performance of the Night Roland Delorme and Justin Scoggins
