Stark must have fallen ill, otherwise it's hard to imagine he would be the one to become General Winter's first victim. Especially since it wasn't even that cold, by the looks of it. Those three did nothing to shield their heads and hands, after all. Anyone with experience of sub-zero temperatures with the additional wind effect knows that's no good. But then again, who knows where the mangaka lives. Probably down south, in Okinawa where the only ice exists in WcDonald's soda cups. Anyway, Fern should have just put a rope around Stark's waist and then used magic to float him.

It's pretty funny they used six months in that random cottage, just like that. It really shows Frieren has a very loose concept of time, with Fern and Stark being infected by her already. Maybe the mountains would have been impossible to cross in deep snow, but in six months they could have visited other places on their side of the mountains.