15-sai & Seiko Oomori (15才と大森靖子) is a Japanese music project centered on singer-songwriter Seiko Oomori, who was born in 1987 in Matsuyama, Japan. Built around Oomori’s distinctive voice and writing style, the project sits at the intersection of alternative pop, alternative dance, J-pop, and rock, with emotionally direct lyrics, a strong personal perspective, and the melodic hooks and raw energy that have shaped her broader work.
As part of Seiko Oomori’s wider artistic activity, the project reflects a creative identity that moves between solo expression and special projects. Oomori’s releases have been associated with Avex Group, and her recent activity has included producing the idol unit Zettai Shoujo and announcing a 47-prefecture tour, underscoring her continued relevance in Japan’s contemporary pop and alternative music scene. The name itself suggests a youthful, character-driven concept while keeping Oomori at the center of the performance and songwriting approach.
