Splatoon 2: Octo Expansion

Splatoon 2: Octo Expansion is paid downloadable content for Splatoon 2 comprised of an additional single-player campaign mode.[1][2] It was revealed during the 8 March 2018 Nintendo Direct and was released on 14 June 2018 at 01:00 UTC with Version 3.1.0. It is the first paid downloadable content for any game in the Splatoon series.

The entrance to the mode is located at the subway entrance in the alleyway to the upper right of Inkopolis Square, next to Deca Tower. It is also listed as Deepsea Metro in the menu.