Crystal is the debut album by Japanese sister duo Double, released on June 2, 1999 by For Life Music Entertainment.

[1] The first press edition of the album came with the CD case with a clear background, and a back insert with the duo posing with the track names on the left side.

Inside the case comes with a photobook with different pages consisting of red, orange, yellow, green, blue, and pink spelling Double letter by letter.

On May 21, 1999, Sachiko suddenly passed away from a subarachnoid hemorrhage at the age of 25 just two weeks before their debut album was released.

Takako was devastated by the loss of her sister and took a break from her music career.