It is such a weird thing that people complain about MC being scare of literal monster. The wyvern is the size of dinosaur, can break stone wall, poisonous, and fast. The adventurers were scare of them. Da fuck you think an office worker gonna react to that. "But he got a Fenrir" that is a battle junkie and can't be everywhere at once, and doesn't remembered to slap the barrier on everytime. He did in fact almost die this chapter. "He should get use to the dangerous world by now" I want you to look up what happen to soldiers coming back from prolonged exposure to war and see how they are "used to it". Dangerous shit doesn't stop being scary, this is not your kirito power fantasy. You can learn to swallow your fear, but it does not goes away.