NiziU announced Monday that it will release its first Korean mini album, Sour Grapes, on September 28 at 6 p.m. KST. The announcement came via a prologue film posted to the group's official social media channels at midnight.

This is NiziU's first domestic Korean release since the single "LOVE LINE" in March 2025, making it the group's most substantial Korean comeback in roughly 18 months. The prologue film centers on grapes as its visual anchor, showing members encountering the fruit across different scenes before shifting into darker, more surreal imagery. JYP hinted that the album's concept revolves around temptation, desire, and curiosity, though the label has not yet shared the track list or revealed which song will serve as the lead single.

NiziU's previous Korean releases have performed well on the charts. The group made its official Korean debut in October 2023 with the single album Press Play, followed by "LOVE LINE" last spring. Both title tracks, "HEARTRIS" and "LOVE LINE," claimed first place on Korean music programs.

Meanwhile, the group has maintained strong momentum in Japan this year. Its second Japanese EP, Good Girl But Not for You, topped Oricon's weekly album and combined album rankings. The group's first Japanese best album, Portfolio, earned Gold Disc certification from the Recording Industry Association of Japan. NiziU also completed an arena tour across five Japanese regions and wrapped its second dome tour, NiziU Live with U 2026 'NiziU : THE CINEMA.'

With Sour Grapes arriving at the end of September, NiziU is positioning itself for a busy fall across both the Korean and Japanese markets.