An ocean-themed unit in hololive consisting of Houshou Marine, Minato Aqua, Ninomae Ina'nis, Gawr Gura, and Sakamata Chloe.
UMISEA is an official hololive unit meant to bring together virtual YouTubers in the production with a common ocean theme and lore under a common name.
Has released a group single in 2021 alongside on-stream collabs in Minecraft and other games. The aforementioned Minecraft collab streams also showed that the two hololive English members (Ina and Gura) were inducted into AKUKIN Kensetsu (though jokingly, Gura temporarily became its CEO for the duration of their collab).
Means sea-sea, as "umi" is the Japanese word for sea.