You've already gotten some great feedback.
Personally, I believe he was justified (as he sees it) initially for his rage, but if he were to express anger again instead of the cold mask he is so comfortable with, it would be him expressing to Kagome that she has the power to incite such feelings in him, and that, for a tactical enemy at least, is the first step to handing over victory, which Sesshomaru would never do. I can easily see him being cold toward her, calm yet deadly, and poor Kagome dealing with the malicious vibe of imminent death should she fail in finding a goat to nurse the baby on, LOL. I don't think he'd lose his temper again, unless it was for a pivoting point in his character. He can overlook his emotions once, but if he loses himself again I'd say you have a good opportunity for character development.
In general, this recommendation is how Sesshomaru is always handled, and it is why he is different in every story. It's because he changes depending on the circumstances. Just jot down where you want to take the story, what event you have planned, and stop writing for a minute. I usually would sit around and listen to a song I felt was fitting for the mood when I was a beginning writer, and thought of words to associate with the character's feelings depending on the situation, even if they're simple, then associating words with those, and making thought chains out of the material. Now, I do it in my head, but initially I wrote it down so that I didn't forget and could go back and use the material for later.
If it helps, here's an example:
Step 1- Bring Kagome back for Rin's sake.
Step 2- He feels: angry, spiteful, pain and remorse, cheated, unjustified, forced into action.
Step 3-
Angry, for how things played out, for Kagome's failure, for not being there, angry at her and perhaps at himself.
Spiteful, she should remain dead for her sins, but damn it just is not that simple, he has to do this for the child, the only thing he has left of Rin, but perhaps not for free, no, he can get back at her for this.
Pain and Remorse, she died, why was she taken away so early, so young, and left to abandon her first and only child, why did she leave him, why can fate be so cruel, why, why, why?
Cheated, it was not supposed to be like this, never, there is so much left to do, so much she did not get to experience, so much she had to leave behind.
Unjustified, the miko deserves what she got, and should remain dead, for Rin's sake, for the sake of justice, but now she needs to be alive, this is absolutely terrible, what the hell.
Forced into action, I have to do this, for the sake of Rin's child, but it is going against my own desires and will, it is not what I wish for but it must be done, how aggravating, how terrible, she should remain dead, so perhaps making her life a living hell will be appropriate.
Step 4- Let your creative juices flow. Sesshomaru's character will change and develop depending on which or how many paths you take him down, and in the end you will own your very own version of him. ^_^ It's a special feeling.
Best of luck to you!
~AD
