North Blue is one of the four major seas in the world of One Piece, a popular manga and anime series created by Eiichiro Oda. It is known for its cold climate and is home to various islands, each with unique cultures and inhabitants. The sea is less explored compared to others, making it a mysterious and intriguing location for adventurers. In One Piece, North Blue is notable for being the birthplace of several important characters, including Nami and Usopp. The sea is also known for its dangerous waters and powerful pirates, contributing to the overall lore and challenges faced by the protagonists as they journey through the world.