Wave 1 was released on 28 February 2023 and added Inkopolis Plaza from Splatoon as an alternate hub world accessible via the subway station found in Splatsville. From here, players have access to services as they originally appeared in Splatoon, including Ammo Knights, Cooler Heads, Jelly Fresh, Shrimp Kicks, and Spyke, although they share the same lineup as their Splatsville counterparts. Certain shops are run by new characters. Additionally, the Squid Sisters perform City of Color (2023) in concerts during the first half of Splatfests and sing Tomorrow's Nostalgia Today during the second half, both while wearing their original outfits from Splatoon. Additionally, the Great Zapfish can be seen atop Inkopolis Tower and the amiibo box retains its functionality. Other features from Splatoon 3 have also been added, such as a Grizzco Industries building and a Tableturf Battle Dojo hidden behind several buildings. The grate leading to Octo Valley is blocked off by a tire and a stack of boxes, while the arcade machine is covered up and replaced with a terminal to remotely access Hotlantis.

In Inkopolis, you'll be able to go shopping at the classic stores from Splatoon 1, but the products will be the same as in Splatoon 3's main hub world, meaning you'll be able to pick whichever hangout spot fits your vibe best. Squid Sisters Callie and Marie will also perform live in Inkopolis during Splatoon 3's Splatfests.