Juubanme no Hime desu ga

Our relationship is all an act, isn't it? I know it's wrong... I may be the princess of a country, but I'm getting lost in how good it feels! "I would be hot even if I weren't a prince, right?" Rosalina, the tenth princess of Phanzam, is saved one day in a rainy forest by Fonhardt, a man from a neighboring country. However, she noticed him getting targeted by an assassin and jumped to cover him, ending up getting shot by a poisoned arrow. Fonhardt was actually the oldest prince of the kingdom of Cresta and was in the middle of a battle for the throne with his younger brother! Rosalina had been pretending to be a maid, but Fonhardt asked her to pretend to be his betrothed to help him reveal the truth about the queen and his younger brother's crimes against the throne. Fonhardt teased her a lot while still showing her his love, and Rosalina ended up falling for him... Source: MangaPlaza