Murmurs of the deep [Splatoon]

Back at Inkopolis Square, some of the cephalopods that lived there had spoken about the murmurs of the deep... it was odd, especially with the fact that there was that odd metro in the square, but yet, a few years later, it was covered up by the Table Turf table... Cephalopods told an Octoling and an Inkling where it was, and that's how they found out it was covered by the Table Turf area... Since it always had people there, it would be too hard to look for the metro where it used to be, so the pair decided to go during the late night on the last train...