Darcy is okay on a boy but it sounds a bit girly to me, I think it’s better on a girl.
I would be careful of using unisex names on boys simply for the reason that most unisex names inevitably become girls names.
Generally a unisex name starts off as a last name that is only used on boys which is thought of as a boys name but then people start using it on girls. It starts off slowly at first, but after about 10/15 years there are as many girls being born with the name as boys and the name becomes unisex, but around that time people begin to stop using the name on boys because they are afraid it’s no longer masculine enough, usage of the name on boys plummets while it continues to increases on girls, and a few years later the name is generally regarded as a girls name.
Also since the sixties all the last names used as first names ending with the letter –y are gradually going from boys names to girls names, (eg Lindsay, Hillary, Haley, Kelsey, Courtney, Shelby, Tracy, Ashley, Stacy, Kimberly, Mallory, Cassidy etc) and I think Darcy, Bailey and Riley are some of the only ones that are still used on boys. All three are already used much more on girls than boys in America, and people are starting to use them on girls too over here so I think it’s inevitable that in the future people will think of Darcy as a girl’s name and will assume girl when they see it on paper unfortunately.
I do think it suits a young guy though, even if it isn't very masculine. smile