Corrin was supposedly born to the Hoshidan royal family as the child of Mikoto and Hoshido's king Sumeragi. As a result, they are the younger half-sibling of Ryoma and Hinoka and the older-half sibling of Takumi and Sakura, who are instead Sumeragi's children with his first wife Ikona. They were kidnapped as a young child fifteen years before the events of the story and raised by the royal family of the neighboring kingdom of Nohr, gaining new siblings in Xander, Camilla, Leo, and Elise. As a member of royalty, Corrin carries the blood of the First Dragons and is able to tap the power of Dragon Veins, allowing them to alter the terrain of a map. However, they are also able to transform into a dragon, in a similar vein to Manakete in previous games. Corrin's transforming powers are awakened during Chapter 5, and they thereafter carry a Dragonstone to secure control of them.

A great war looms over Hoshido and Nohr, and the two kingdoms soon meet on the battlefield. Corrin must choose to join with one of the kingdoms and help with their respective causes or remain neutral in an attempt to combat a larger threat. Corrin has the services of Silas, Gunter, Kaze, Felicia, Flora, Jakob, and Lilith. If Corrin achieves an S-Support with any opposite gendered character, they will have a child named Kana, whose gender is the opposite of Corrin's. Male Corrin can also be the father of Shigure, while female Corrin can be the mother to all of the children characters aside from Shigure.