I Do! Do You?

"I Do! Do You?" is a song recorded by South Korean girl group Kep1er for their second Japanese maxi single marketed as "Fly-By". It was pre-released as a digital single on February 21, 2023, and as a CD single featuring three other tracks on March 15, 2023, by WakeOne and Ariola Japan.

Background and release
On January 16, 2023, Wake One Entertainment announced Kep1er would be releasing their second Japanese maxi single titled "Fly-By" on March 15. The maxi single features four tracks including "I Do! Do You?". "I Do! Do You?" was pre-released alongside its music video on February 21. The maxi single was released on March 15.

Composition
"I Do! Do You?" was written by Tsingtao, and Ryo Ito, and composed by Jonatan Gusmark, Emily Yeonseo Kim, Moa "Cazzi Opeia" Carlebecker, Ellen Berg, and Moonshine. It was described as a "uptempo" dance song characterized by "funky disco rhythm" with lyrics about "[Kep1er]' members subtle feelings about the person they like and their growing feelings". "I Do! Do You?" was composed in the key of C major, with a tempo of 120 beats per minute.

Commercial performance
"I Do! Do You? debuted at number three on the Billboard Japan Hot 100 in the chart issue dated March 22, 2023; on its component charts, the song debuted at number 86 on the Top Download Songs. The song debuted at number three on the Oricon Singles Chart, and the Oricon Combined Chart in the chart issue dated March 27, 2023.

Promotion
Prior to the release of "Fly-By", on March 6, 2023, Kep1er performed the song on CDTV! Live Live.