Seifer is the type of tsundere that relies on making it clear that he does not care what you are saying. Of course, the dere part of it is that he does in fact care to some extent, depending on the situation.

...Though there are times when he actually does not care, so you must be careful.

If he is angry, however, it is very serious! Surely you have stepped over a line. Ah, if he does not act as if he does not care, actually, it is probably a sign of something...

[trailing off to ponder]