Shinro Denka no Saiaihi (Dakedo Watashi, Honmono no Tsugai ja Arimasen!)

I was reincarnated as a villainous princess who becomes obsessed with the "Divine Wolf Hero" and is killed!? Luna, the youngest princess of a small country, realizes that this is the world of a novel she read in her previous life. the divine wolf prince Rudolf can't find a mate. Love is needed to stop his rampage, but the "real heroine" who plays that role in the novel loses her life. The murder of the princess repeats. Luna, destined to be hated by Rudolph, is ordered by him to "play the role of a fake mate"... but for some reason, he ends up falling in love with her to the point of drowning!? (Source: Kodansha, translated)