Asakiyume mita

That's true, but I'm bothered by my lack of reaction, I guess. Sometimes I feel very inhuman.

I don't think that's a useful way to think of it. There are conventions of human emotion and reaction and very few of them, as far as I can tell, map on the multiplicity of real human emotion and reaction as opposed to the training that people receive in how to present or mask themselves so that other people can read them. It would be a different question if we were talking about a consistent lack of empathy, or the inability to recognize even intellectually the existence of other people's pain. (I am a big proponent of the fact that you don't need to be physically upset by someone else's distress to decide to do something about it.) Since that's not at stake, don't beat yourself up, or allow societal expectations to do the beating for you. I have been called not human because of some of the things I am not upset by. Unfortunately, since no extraterrestrial observers have yet claimed me, I am forced to conclude the spectrum of human emotion is just very wide.