Probably thinking of Acting Lessons, which had the MC's best friend as black, a super cool dude if I remember correctly, been awhile since I played that one. Being A DIK has some black frat members the MC is cool with, no NTR vibes, but they are more secondary characters (or were, again haven't played that one in awhile).
Unfortunately the black guy usually falls into rude idiot with giant hypnotizing dick category in a lot of porn. I can't really think of many other games that feature a black friend, or similar. The Lewdest House has his black friend, who plays a minor part for the plot, that may fit. Shoot, now you got me thinking of how many games feature a black friend or co-worker etc. that isn't an NTR flag.