NiziU released a performance teaser on September 18 for 'Sour Grapes,' the title track from their upcoming first domestic mini-album. The video showcases choreography set to an upbeat instrumental described as sounding like popping grape seeds, with members executing dynamic, large-scale movements and sharp gazes. Vibrant lighting and styling frame what JYP Entertainment is presenting as a notably different visual direction for the group.

The teaser arrives as NiziU wraps an active year of live performances. The group completed a five-region, 12-show solo arena tour called "NiziU Live with U 2026 'NEW EvoNUtion'" across Japan earlier this year, followed by the successful conclusion of their second dome tour, "NiziU : THE CINEMA." These shows have given the members opportunity to refine their stage presence ahead of this new release cycle.

NiziU's track record with title tracks has been strong. Their debut song 'HEARTRIS,' released in October 2023, earned them a music show trophy, as did their second single 'LOVE LINE, Destiny Line' in March 2025. The group is returning with upgraded performance skills and what the label describes as a noticeably fresher sound and concept compared to previous releases.

'Sour Grapes' officially releases on September 28 at 6 p.m. through major streaming platforms. The mini-album marks a new chapter for the group and represents what JYP is positioning as a deliberate shift in artistic direction.