Manga Like Watashi wo Suki Sugiru Yuusha-sama wo Riyoushite, Konse koso Nagaikisuru Tsumori datta noni (Tabun, Mata Shippaishita) 

"Please, use me as you wish." Lizette, a count's daughter, is a "Recaller" who remembers her previous lives, and she is now on her fourth life. In her past lives, always on her 20th birthday, she would be killed and eaten by the same demon. So to live a long life this time, Lizette retreated to a remote countryside sanctuary, where monsters don't appear, living quietly and peacefully. But one day she met Ralph, a boy she saved in her childhood. Somehow, he had become the country's hero by defeating a demon lord. If she could stay by Ralph's side, she might not have to die this time... With this in mind, Lizette accepted his proposal. "I will protect you, Lisette-sama, even if it costs me my life." While bewildered by Ralph's exceedingly heavy affection, Lizette uncovers the truth behind her repeating deaths. Will Lizette be able to live pass her 20th birthday unharmed this time?! It's the start of a romantic comedy between the heroine who doesn't want to die and the intensely doting yandere hero! (Source: Comic Brise, translated)