NMIXX is set to release their fifth mini album, titled "Heavy Serenade," on May 11, 2026. The group heightened anticipation for this album by unveiling a promotional trailer video on April 21st. In the trailer, the six members convey their feelings of love through various vignettes. Sullyoon shares precious items to create a romantic atmosphere, while Lily is depicted running with a letter, eliciting curiosity. The other members, Haewon, Jiwoo, Bae, and Kyujin, contribute to the emotional depth through individual narratives that capture their personal arcs. The trailer culminates in a lively scene where all members gather to share a "serenade" filled with laughter and music, suggesting a rich thematic exploration within the album's content. To build momentum leading up to the release, NMIXX plans to showcase track performances and music videos in succession, creating a dynamic lead-up to the album launch.