In addition to the bonus What IF stories, Re:Zero author Tappei Nagatsuki went back and wrote a series of short stories set between the second and third arcs, developing Rem and Subaru's relationship. The second of these was Mayonnaise Scramble, in which a certain popular oni learns how to make the condiment. (The light novels establish that Subaru is from a family of mayo enthusiasts).
Manga adaptation artist Makoto Fuugetsu had been begging for a chance to adapt this. And, In the new issue of Bin Gangan, she gets her chance.