It feels odd to have my first post on this form be one about asking for help, but oh well....
I got the PSN version of this game and I'm really getting into the Vita version, you can probably that Deceased Crab for that.
The thing is, I think I've been doing pretty great so far, I'm slowly mapping the whole game and until now I never needed help to find a secret area.
The area I'm trying to get to is 43,9 and I'm positive I can access it from 42,9 and yet... even though I can practically see the entrance it's actually a wall. It's probable that the red powerup in the area is a clue to get into there, but I have no idea how...
I even looked at a map and everything indicated it should be there. Here's the map with the area I'm trying to reach.