Tsurugi Seijo Adel no Yarinaoshi

A blind swordsman ended a devastating war that had ravaged the continent. His power stems from painful memories of brutal experiments and deadly combat. Princess Euphinia helped him find peace, and he vowed to protect her. Despite his efforts, he failed to save her at a critical moment, leaving him with deep regret. He longs for another opportunity to correct his mistake. A mysterious entity offers him one wish, and he seizes it. He is sent back in time, but awakens as a woman. Using his swordsmanship and new abilities as a Saint, he begins working to alter history and rescue the princess.