NiziU is bringing momentum from their successful Japanese releases to the Korean market with the mini album Sour Grapes, arriving September 28 at 6 p.m. KST.

The group has mapped out an extensive promotional calendar that kicked off with an online cover on September 10. Concept photos roll out from September 11–13, followed by an album detail preview on the 14th and tracklist reveal on the 15th. Concept films arrive on the 16th and 17th, with a highlight medley premiering on the 24th.

Three dates—the 18th, 21st–23rd, and 27th—are marked with question marks on the scheduler, leaving fans to speculate about unreleased content that might be coming their way.

This marks NiziU's Korean comeback roughly 18 months after releasing the single LOVE LINE in March 2025. The album's title references Aesop's fable The Fox and the Grapes, suggesting a thematic concept the group plans to explore musically and visually.

The timing capitalizes on NiziU's strong run in Japan this year. The group dominated local charts with their second EP Good Girl But Not for You and their first best album Portfolio, and completed successful solo arena and dome tours that demonstrated their growing fanbase. By carrying that momentum into Korea, NiziU is positioning themselves to establish a presence with Korean audiences while maintaining their Japanese platform.

Sour Grapes represents the group's first official Korean mini album release, signaling an intentional expansion beyond their established Japanese market presence.