Yomei 1-Nen, Shinigami to Tanoshimu 10 no Koto

Since childhood, Eleonora, the daughter of a marquis family, has strived to behave as the head of the family. Now afflicted with a heart disease that leaves her with only one year to live, she becomes engaged to a partner without ever knowing love. On the day of her engagement, she falls in love with a mysterious, enigmatic man. The true identity of this man is a "Death God" who has come to claim Eleonora's soul in a year. "I'll grant you ten wishes before you die," he says. He reaches out to make her remaining short life the happiest year of her life. Original Webtoon