She has fought in MMA promotions Shooto, Jewels and Rizin in Japan, and Invicta FC in the United States.
Hamasaki won the first Jewels 115 lb (52 kg) Queen tournament to become the first lightweight champion of the promotion.
[16][17] At Jewels 11th Ring on December 17, 2010 (2010-12-17), Hamasaki defeated Sakura Nomura after three competitive rounds via unanimous decision in the Lightweight Queen tournament semi-finals.
[18][19] Hamasaki was scheduled to face Lisa Ellis in a non-title bout at Jewels 12th Ring on March 11, 2011 (2011-03-11) in Tokyo, Japan.
Hamasaki was then set to face Jessica Aguilar at 12th Ring instead,[21] but the event was cancelled after the Tōhoku earthquake and tsunami earlier in the day.
[49] Her second title defense took place against Jinh Yu Frey at Invicta FC 19: Maia vs. Modafferi on September 23, 2016.
[50] She then faced Lívia Renata Souza in a strawweight bout at Invicta FC 22: Evinger vs. Kunitskaya II on March 25, 2017.
[51] Later in 2017 Hamasaki vacated her Invicta FC Atomweight title and subsequently signed with Rizin Fighting Federation.
[53] Ayaka defended her title for the first time against Invicta FC Atomweight Champion Jinh Yu Frey at Rizin 16: Kobe on June 2, 2019.
[55] Ayaka faced former Road FC Women's Atomweight Champion Seo Hee Ham at Rizin 20 on December 31, 2019.
She lost the trilogy fight via split decision, losing the Rizin Women's Super Atomweight Champion in the process.
[57] Hamasaki next faced three time freestyle wrestling World Champion Miyuu Yamamoto on December 31, 2020 for the vacant RIZIN Super Atomweight belt.
[62] Hamasaki faced the reigning Jewels Strawweight champion Seika Izawa in a non-title bout at Rizin 33 - Saitama on December 31, 2021.
[64] Hamasaki made her second Super Atomweight title defense against Seika Izawa at Rizin 35 on April 16, 2022.
Hamasaki faced the inaugural WSOF Women's Strawweight champion Jessica Aguilar in the tournament quarterfinals which were held at Rizin 37 - Saitama on July 31, 2022.