Futago no Akuma to Tsugai no Tsuki

Luna, a childhood friend of the devil twins Yui and Nagi, has been living as the future "mate" of her beloved Yui. However, when they meet again by chance, Nagi forces Luna to make a "mate" contract, and while her heart still loves Yui, her body becomes aroused by Nagi..!? Yui is a kind, twisted devil, while Nagi is a selfish, forceful devil. Who is Luna's destined mate? A love triangle fantasy of stealing and being stolen from each other!! (Source: Shogakukan, translated)