The official Twitter account for Aya Kanno's Requiem of the Rose King (Bara-Ō no Sōretsu) manga has announced that the TV anime adaptation of the manga will premiere in Fall 2021.
VIZ Media publishes the manga in English and describes it as:
Richard's father, the patriarch of the House of York, is poised to become king of medieval England during the bloody Wars of the Roses. But just as success is imminent, he is abruptly cut down. Plunged into despair, Richard acts out in revenge and must face a powerful and beautiful new enemy.
ANNOUNCEMENT PV:
FIRST AND FIFTEENTH VOLUMES:
Richard's father, the patriarch of the House of York, is poised to become king of medieval England during the bloody Wars of the Roses. But just as success is imminent, he is abruptly cut down. Plunged into despair, Richard acts out in revenge and must face a powerful and beautiful new enemy.