Read this guide on how to get back to the Sewer System in Final Fantasy 7 Remake (FF7 Remake, FF7R). Including how to unlock the path back, and reason!!!
How To Return To The Sewer System
Progress the Story In Chapter 14
As you proceed the main story in Chapter 14, where you track down a Shoats into its den with Leslie. The den will be located in the Sewer System itself, and after confronting the Shoats, Leslie will lead you through the sewer, and unlock a new entrance for you. Be sure not to follow Leslie all the way to the end as it is a point of no return.Check Out Chapter 14 Map & Guide
Why Come Back To The Sewer System?
Find Part Of Corneo's Secret Stash Here
One of stash, a part of Corneo's Secret Stash Odd Job side quest, can be found in this location. As mentioned, this place will not be accessible until you further progressing into the Chapter, be sure to pick up the quest prior and pick up the stash while you venture here.More On Corneo's Secret Stash Here