I have five romex wires going into a single outlet box. However things are a bit messy and I don’t understand the wiring scheme or any scenarios that this would account for. So here is the layout
4 of the romex wires are setup exactly how I would assume. They are wire nutted together neutrals(white) together, hot (black) together, And then the grounds. Here is where it gets funky. The fifth romex cable has the black wire going to neutral side of the outlet and the white neutral wire is twisted with the other four black wires. So then there is a black pigtail going from the four white wires to the hot side of the outlet.
Lastly receptacle says 15a on it but breaker says 20a so even that is strange as I would think the outlet would Burn up first.
I also tested this with a outlet tester and it came back as correctly wired. House is built in 83.