@Minh All you said is partially true. But, see the situation a bit objectively. He has killed many in the previous wars he fought, yes. But he never lost any of his classmates no matter how difficult the fight was (although because of mc's planning). He wasn't ready for anyone close's death. He might even have this fantasy in his subconscious mind that everyone would return to earth without anyone dying.
This is him facing the dark reality. So yes, this outburst is expected.
This is him facing the dark reality. So yes, this outburst is expected.