It looks like Sekiro's current outfit isn't to everyone's liking, so if you fall into that camp, you now have a choice in garment. Although the mod is called Black Sekiro, it actually carries two color variants of The Wolf's costume: black and white.
When Sekiro wears black, he looks like a real ninja, which makes him pretty badass. But if you prefer a noble white robe, then you have that option, too. Additionally, the white robe has the added effect of making Sekiro totally invisible in the snowy landscapes of ancient Japan.