Bolbbalgan4 began its comeback in earnest by releasing all concept teasers for Shinbo's "Butterfly Effect."

BOL4's agency, Shofar Entertainment, released the last concept moving teaser of "Butterfly Effect" on its official SNS channel on October 21st.

Following the first moving teaser released earlier, a unique teaser that shows the members, lyrics, and Ahn Ji-young's atmosphere that connects the past and the present, allowing them to infer clues about the new song.

The single "Butterfly Effect" will feature two songs, "Butterfly Effect" and "You Were My World," as in the previous albums, both songs were written and composed by Ahn Ji-young, and the Vanilla Man. Who has been working together, participated in joint compositions and arrangements, participation raised expectations even more.