The Ruby is the sixth extended play by South Korean girl group April.

[2] Being in black and white, Osen noted that the promotional poster differed from April's previous imagery as it lacked any primary colors, and noted that the band had evolved and matured with each release, "adding a variety of changes to every album".

My Mistake" was released along with the EP on October 16, with Billboard calling it a "revitalizing dance track that adds a new side to April's artistry", as well as "unconventional" and describing it as having a "rollicking '80s-esque scattered beat and quirky, cloying lo-fi vocals over vibrant synths".

[1] The magazine also said the video "takes the audience back to the yesteryears of VHS tapes, corded phones, and RAZRs".

[1] The Ruby debuted at number 10 on South Korea's Gaon Album Chart, while Oh!