I am probably too late to add my input…but I shall
First off, I wanna say I enjoy ‘dark’ themed stories. Now, that being said, I do not like when the male protagonist (a.k.a. Sesshomaru in this instance) rapes the female protagonists (a.k.a. Kagome) for a few plot reasons.
#1: In my mind, it is impossible for the victim (and yes, that is what the raped individual is) to go from hating, fearing, and being mistrustful of her rapist to falling in love with him—ever. So if the author wishes to put a romantic theme in his/her story, being raped by the would-be spouse/mate is grossly unrealistic (even though Sesshomaru wasn’t himself). The plot suffers mightily.
#2: I am on the fence about Sesshomaru ever losing control of himself because of how his character is already set up. Unless of course it is an A/U story or there is a VERY reasonable cause to make him lose control. But let’s say he does lose control. I do not see how someone who was basically forced (through insanity of losing control) can stand the thought of being a rapist, let alone going a step further and in the end becoming married/mated to his victim.
#3: Going this route in any story lowers readers (let’s say woman of all ages right now) self-awareness of the atrocity that was done to them. When the rapist and victim end up in a ‘happily ever after’ it falsely tells women that they NEED to forgive and forget because their rapist is mournful and regretful of his actions, so let’s forgive him and start up a real and intimate relationship. Basically, it belittles what they went through.
#4: This follows along with #3, actually. The ‘out of his mind’ rapist ‘who didn’t know what he was doing’ portrays that, no, his actions weren’t as horrible as it really is. Basically, oh she forgives me, so it’s ok if I go into an intimate relationship with her.
So, the trust id gone for the victim and the rapist is filled with regret. There is no way, in my mind, that these two can ever build anything in a relationship with these issues about one another. Having a ‘dark’ them does not mean the male/female protagonist is raped by the other male/female protagonist. ‘Dark’ can be portrayed in many ways that will work with the plot and make it cohesive and solid.
Since this is my view point, I will never read, let alone like, a story of any kind, published or not, where a victim falls madly in love with her rapist.
My next point:
Now if the woman (Kagome) was raped in the past by someone else and then slowly builds trust towards the male protagonist (Sesshomaru) than that is a solid plot with this particular dark them you seem to desire.