>>536332405
Look back to Mizuki's middle school edgelord phase. That did not disappear. It came out when Mafuyu was telling niigo that they also wanted to kill themselves. Mizuki's reaction to being offended is not running away he will confront you. Another manifestation of that is Mizuki doesn't open up at all. He can endure being othered a lot because of this resilience. When he finally decides to be vulnerable and open up to Ena, he was punished for it. It reinforced his fears and that's why he completely shut off.