Klein's first target of suspicion was undoubtedly Elf King Soniathrym.
This ancient god had created chopsticks, made blood cakes, enjoyed eating animal innards, and was good at using spices for cooking. "His" descendants had facial features, hair color, and eyes that resembled Asians on Earth. Not only did Klein suspect that "He" was a transmigrator, even Emperor Roselle shared his feelings.
Of course, after a deeper level of investigations, Roselle had ruled out that hypothesis from their language, symbols, traditional proverbs, and other facets. Klein believed that using chopsticks as cutlery, the preference for eating innards, and using spices wasn't an exclusive trait. To a species that enjoyed nature, it was possible for these to gradually appear in their daily life!
As for why elves who wielded the Sailor pathway were close to nature, Klein didn't know why. It was just something as described by the murals and texts they left behind.