I think almost any Isekai anime would be strange for someone who doesn't watch anime, but personally one of the ones I found the strangest at the beginning was Senyoku no Sigrdrifa, humanity is attacked by strange creatures from pillars that appear without explanation, young girls with pilot suits are the only way to fight, for some reason they use planes from the first world war and also turn out to be the famous Valkyries from the nordic mythology, all very peculiar indeed hahahaha
