Spoilers for episodes 80 & 81.
Note: I had a particularly weird time writing this chapter. It's so important to their story, so I couldn't just skip over it, but it did happen in the anime. Even if I put dialogue in, it would just be a creative transcription, still a summary of things that happened. And I couldn't think of anything else that could be happening around these episodes, since Sesshoumaru and Rin have more than just a few minutes of screentime. So I opted to focus more on thoughts, than what is actually happening, since we know what happens. Anyway...
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It had all started out as a perfectly normal day.
It had all been perfectly routine. Rin had gone out to look for food, and Jaken had gone with her. But only Jaken had returned, groveling and apologizing and managing to get out in between all this that Rin had been taken. Then Naraku had appeared, and had 'suggested' to Sesshoumaru in a roundabout way that he should go kill Inuyasha.
Sesshoumaru disposed of the puppet and then turned and began slowly walking in the opposite direction. He didn't know what made him angrier, or what should have made him angrier. That Naraku was trying to use him again, that Rin had been taken, or that Naraku had the impudence to think that it would work. But he could sort all of that out later. Right now, only one clear thought was on his mind: kill Naraku.
Naraku's scent was steadily drifting from a far point in the distance. It was obviously a trap. Sesshoumaru knew that it was a trap, and knew that Naraku knew that he would come anyway. But he didn't care.
He fully intended to kill Naraku. Unfortunately, for some inane reason, Inuyasha arrived out of nowhere with the same objective. Whatever reasons the hanyou had for wanting to kill Naraku, Sesshoumaru didn't care. But none of it had lasted long. Naraku refused to fight with both of them at once, and took the coward's way out. It wasn't until Naraku was gone that Sesshoumaru realized why Rin had really been abducted. Naraku had taken her to provoke him, certainly, but also to make time to run if things didn't go as planned.
What infuriated Sesshoumaru more was the fact that Naraku had known that he would get Rin instead of chase after him. Wait--why did he have to go after her? He could still catch Naraku, kill him, and end this now. But he wasn't going to. Sesshoumaru didn't know why, exactly. He realized that Inuyasha was babbling about something, but he didn't really care to pay attention.
Sesshoumaru left. He soon found her, along with some human underling of Naraku's. At least he would get to kill someone over this. But Inuyasha appeared again. Apparently he had some interest in the brat not getting killed, and was even prepared to fight over it. Well, that was too bad for Inuyasha. Sesshoumaru moved to the brat, but realized that he wasn't putting up a fight. Naraku's underling didn't care if he lived or died; in fact, he seemed to be doing his very best to get killed. Sesshoumaru dropped him. He wasn't doing anything else that Naraku wanted that night, no matter how personally satisfying it might be.
Then he collected Rin and left. As much as he didn't care to converse with his brother, he particularly didn't care to converse with him tonight.
Rin seemed oddly unfazed by it all, which also annoyed Sesshoumaru to no end for some reason. She was asleep by the time they stopped a short while later. (And Jaken had had the rare good sense to recognize that Sesshoumaru was in a fouler mood than usual, and had remained quiet.)
That night, two people had predicted exactly what he was going to do. Sesshoumaru had known that Naraku was setting a trap, and he hadn't been concerned. However, the extent of the planning behind that unsuccessful trap had been successful. Naraku hadn't obtained his objective, but he had gotten Sesshoumaru to do exactly what he wanted, on several accounts. And Rin had known that he would come as well. They both knew, though Sesshoumaru himself hadn't known until he was already acting. It was one thing for the girl to have her misplaced (or not so misplaced) trust in him, but to have Naraku read him so transparently was galling. That, plus Naraku's previous meddlings, earned Naraku the top place in his priorities.
But what was also annoying was the different rage that he had felt when he had arrived to find Rin about to be struck down by that brat. Sesshoumaru realized that he had wanted her to be all right. And he absolutely loathed the realization.
Evident now more than ever was the fact that she was a liability, a disadvantage, something that could effectively be used to manipulate him. The logical thing to do would be to get rid of her somewhere, but he knew that he couldn't. Somewhere along the line, she had made him care. Somehow, she had taken sheer morbid curiosity on his part and turned it into making him actually care about what happened to her.
She was nothing, she shouldn't be anything to him. So why was she? How could she have done that to him? To him--he who had always looked down on pointless attachments and prided himself on being above succumbing to that sort of meaningless idiocy. And so easily she had done it. He wanted to hate her for it. He absolutely wanted to hate her for it, but he couldn't. That was the problem with having a weakness--if one could do something about it, then it wouldn't be a weakness.
Damn her. Damn Tenseiga. Damn everything.
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Note: I would have liked to end this chapter on a more uplifting note, but as I wrote it, I realized that I couldn't. Really, this is the first time that Sesshoumaru is really confronted about Rin, and probably the first time that he really realizes that what he had suspected was happening with her has happened. He never wanted to care, and it's too late to do anything about it. And I can see him being pretty pissed off about the whole thing.