[4] On October 27, 2020, Cube Entertainment released a video informing BtoB's new unit name through its official SNS channel.

[5] On October 30, Cube officially announced their debut date with the album name and released an artwork teaser image of a vintage door where sunlight and clouds on it.

Even when we remain the color of full BTOB, but we included the energy that only four of us have, 2 vocalist, 2 rappers, the balance make the stage more harmoniousDuring the group's debut showcase, Changsub confessed that "After the military discharge, I devoted myself to this album.

"[9] The second track, "Tension" is composed by earattack, Jimmy, eniac and Jwa Young Kim.

The song is described as an ear-pleasing R&B track led by a simple, addictive acoustic guitar riff with a trendy arrangement along with a moderate beat and slick synth.

The song matches with the personalities of the members who are famous for their talents and energy, individual charms and capabilities are revealed boundlessly that can feel the energetic identity of BtoB 4U.

In "In" version, the group showed their luxurious visual with chic and serious charm and poses with a black jacket and shirt under a dark turquoise background.

[11] In "Side" version, the members shows their unique charms wearing casual and colourful outfits and the use of different props such as smiley balloons, toy airplanes, dinosaur dolls, popcorn, and flower-shaped sunglasses different from the first concept image released.

[4] During a YouTube live stream on November 16, Eunkwang revealed that "During the jacket filming, they were told to design the CDs.

"[10] Choo Seung-Hyun of the Seoul Economic Daily wrote in his review "Unlike many groups that usually show 180 degrees of different concepts while forming units, BtoB emphasized its unique pleasant and positive energy.

[17] On November 2, 2020, Cube released a time table for BtoB 4U's first extended play through their official homepage and SNS, which shows the group's promotion schedule beginning November 4 until their first online concert, 2021 BtoB 4U Online Concert [INSIDE] on January 23, 2021.

[20] On November 16, the group held an online media showcase for the release of Inside at the YES24 Live Hall in Gwangjin-gu, Seoul,[7] hosted by broadcaster Ha Ji-young.