Seiko Oomori (大森靖子; Oomori Seiko) was born September 18, 1987 in Matsuyama, Ehime, Japan and is a singer-songwriter who has done solo work and has been in the duo Oomori Seiko & THE Pink Tokarev (disbanded in 2015), as well as a new idol project called ZOC (the group would rename to METAMUSE in 2022).

Aside from writing music for herself and her groups, Oomori has provided music for other artists as well, such as those in Up-Front and Hello!Project. One such artist includes one of her idols Sayumi Michishige (former Morning Musume member).