The armor and sword were probably made with the Alchemy Authority if the metal can't melt or be processed in anyway, so it looks like Shizuka is gonna get some fun material to work with
The alchemy authority was described as automatically gathering materials nearby... I wonder how fast that is. Maybe she can use the authority to try and make her own orichalcum equipment, and the authority just goes "oh, hey, there's a bunch of orichalcum nearby... Yoink!"
Assuming even the chainmail at the joints is orichalcum then I guess all that's left is the eye slit. Unless that's orichalcum glass in there. Then I guess it's alchemy up some poison gas, he's got to be breathing somehow.
And if anyone can produce a powerful sustained fire attack, then Mr. Lawful-Dum just provided a convenient air-fryer. Or are they going to use the Orihalcum-armor-can-disperse-fire-away-from-its-wearer BS?
The armour can easily be cut as they foolishly left the joints uncovered by the metal and even if they still can't cut the armour they can just wait 5 minutes, then he'll be completely inable to move due to overheating.
It's Magic™ Isekai/Fantasy armor.... One does not overheat in those and one can wear it 24/7 without any ill effects at all.. Nor do those stupidly large pauldrons have any actual mass, and that headband protects against slashes against the torso, and......
Even if the joints were covered with Plot Magic™ MC can eaily cut the inside ... It's a sort-of bascinet... The eyes are not covered... by a ridiculously large eye slit... stabby-stab, and done....