Himebusho Masamune Den Bontan!!

A young girl in the Date family is born with a spirited and energetic nature typically associated with boys. In 1571, she contracts smallpox and nearly dies, resulting in the loss of sight in her right eye. Her parents use this event as a chance to change her status, convincing her that she is actually their eldest son, Bontenmaru. From this point, she is raised as a boy and begins a life that mirrors the legendary story of Date Masamune.