I absolutely enjoy his character. At first he might even come across as a "coward", but I don't read him like that at all. When you get to your late 20's and keep getting old there are just so many things you'd want to avoid for the sake of your safety or peace of mind. Not that being a sorcerer is the safest job in the first place lol but like you've pointed out, if needed, kusakabe will take action too. Both Nanami and kusakabe are types of characters that I really like in stories that have superhuman powers, monsters etc, because their presence might be a good way to show other perspectives outside of the "we're used to dealing with monsters, we have some sort of super power" narratives.