Photos of white-yolk boiled eggs have gone viral on Japanese social media, with thousands of people asking whether they are real or just digitally altered.

It all started with an X (Twitter) post by Tsuda Junko, the editor-in-chief of the online magazine Design no Hikidashi, featuring a photo of a boiled egg cut in half. It doesn’t sound like the most exciting post ever, but it ended up going viral for a very intriguing reason – the cooked yolk was about as white as the egg white around it. Junko himself expressed his astonishment, claiming he had heard about this variety of Okinawa eggs with white yolk but never imagined it could be this white.