The Archrival Duke Won't Let His Spy Fiancée EscapeNewあくまで、婚約任務です！～宿敵公爵様はスパイ令嬢を逃がさない; Akumade · Konyaku Ninmu desu! ~Shukuteki Koushaku-sama wa Supai Reijou wo Nigasanai

"Shall we spend our lives together?" Grace, a young woman who secretly serves her country, plays the role of a public villainess while working as a covert spy. She accepts a one-year engagement mission with Felix, the young head of her family’s sworn enemy, after being promised her first-ever vacation bonus upon completion. During this time, she’s also tasked with protecting Felix, thinking, “Since our families don’t get along, it’s better if we keep hating each other so I can focus on the mission!” But for some reason, he starts becoming strangely attached to her...!?