Independent and dependent variables, I assume. As otherwise, you are indeed likely to find nothing

What you can try here is run a quantile regression (QR) -- one that would allow you to estimate the impact of your predictor on the DV in the lower (e.g., 10th) or higher (e.g., 90th) percentiles of the distribution, if that is what you are looking for.

Check this paper to get a sense of what QR is all about: Cade, B. S., & Noon, B. R. (2003). A gentle introduction to quantile regression for ecologists. Frontiers in Ecology and the Environment, 1(8), 412-420.