In 1999, Crystal Kay made her debut with "Eternal Memories".
Her third album "almost seventeen" released in October 2002 debuted at No.2 on the ORICON chart and she achieved a major breakthrough with hit songs such as "Boyfriend -partⅡ-" and "Koini Ochitara". Not limited to J-POP, she expanded her musical styles to diverse fields such as R&B and HIP HOP, establishing the "CK Sound". She continues to evolve as an artist transcending race, gender, and age.

She appeared in the Broadway musical "Pippin" in 2019 and 2022, winning the Best Actress Award at the 27th Yomiuri Theater Awards. She also focused on acting, appearing in the movie "Between the White Key and the Black Key" in 2023 and in the Broadway musical "RENT" (collaborated by Japan and America) from August to September 2024.

She celebrated her 25th debut anniversary on July 1, 2024, released her latest song "Love Myself" in November, and held the 25th anniversary live show "CK Ni Go ~25TH ANNIVERSARY" in December at KT Zepp Yokohama in her hometown, Yokohama. BoA from South Korea and m-flo from Japan appeared as guests, and the venue was packed to capacity, making it a truly spectacular live show where she celebrated her 25th debut anniversary with fans.

In June 2025, she released her 1st ALL TIME BEST album "ALL TIME BEST 25th Anniversary".
In August, she successfully completed her first tour in America (7 shows in 7 cities).

She celebrated her 40th birthday on February 26, 2026 and held her first birthday live show "Birštonas presents CK BIRTHDAY BASH LEVEL 40" at KT Zepp Yokohama in her hometown, Yokohama once again, with an impressive lineup of guests (EXILE SHOKICHI, Zeebra, Mummy-D (RHYMESTER), SWAY, JIMMY+WEESA (PSYCHIC FEVER), Kinjo Sukai (JO1), Daichi Yamamoto, Lucas Valentine). She continues to be active both domestically and internationally, acting as a bridge between Japan, America and South Korea.