It doesn't seem dark at all to me, not even compared to the other things that I've seen posted here that people say are too dark. But even aside from my own perception there are a few mitigating factors to anything being "too dark" in KS+. Most people will be playing things at the very least at 2x zoom, which would alleviate most every concern of things being difficult to interpret, I think. Also, hiding the desktop again makes any darkness easier to deal with. But this is just how I feel, where darkness as a concern is only really relevant if the player can't proceed through the level because of the darkness or see things they are intended to see.
Not to say that this even comes to the level of having any difficulty in interpreting its graphics at all, from my perspective. At no zoom, on this forum, contrasting the brighter default skin, I can see fairly plainly that its Juni and a car at the edge of a forest. I think to ask yourself if it should be changed is if it is absolutely necessary for the player to see for progression or at least would it make the experience of the player better being able to interpret the forest in this screen by being able to distinguish each tree that is in the background. To me, it seems to work better as the background hills are close in color to the background trees and bushes, from easily distinguishable to less so at the end, giving the impression of something shrouded and brambled that you're walking into. If the issue is distinguishing each element I would change the background hill color to be overlayed/colored similarly to the dark blue sky, so that the background hills would be blueish to contrast against the brown of the background trees and bush. I think the issue people are having is distinguishing similar colors and not necessarily darkness, though, again, it still looks fine to me as is.
And to LPChip, the car being a placeholder can be ignored, Juni should be darker, I agree. I think a darkened version of Juni would be better to start the level with and then brightened upon entry into the house which I assume would be brighter, or not, as Juni's white (or grey for a darkened Juni) contrasts perfectly fine and distinguishable against everything in the outdoors that I saw in the alpha and probably most everything that would be in the level given the color palette I've seen so far. I think using the custom character feature in KS+ as a means to employ lighting differences for Juni is an excellent way to give a better impression of a darker atmosphere that can be changed fairly seamlessly as Juni approaches a light a shift changing her to a brighter version of the spritesheet can be used and a shift to a darker version of Juni as she walks away from the light, I've used this for several things and it works pretty well to give an impression of lighting on the character.