[4] Sun Dance and Penny Rain were Aimer's first new studio albums since daydream in 2016.

[6] In February 2018, Aimer thought about a concept for her next album after releasing her single "Ref:rain".

She then came up with the concept of "Sun and Rain" and used it for her "soleil et pluie" Hall Tour from October 2018 to January 2019.

In contrast to the lively and up-tempo themes of Sun Dance, Penny Rain features darker themed tones and more ballads, with the lead track "I beg you" incorporating a Middle Eastern rhythm.

The album also features collaborations with Yuki Kajiura, Cocco, TK, and Hiroyuki Sawano.