Corrin is the child of Mikoto the second queen of Hoshido and is allegedly the child of 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. As proof of their royal heritage, Corrin carries the blood of the First Dragons, allowing them to tap the power of Dragon Veins. In actuality, Corrin was born to Mikoto and the human manifestation of Anankos' benevolent soul in Valla. However, their happiness toward was short lived as the dragon form of Anankos began his rampage, forcing Anankos' human form to send his lover and child to safety. Eventually, Mikoto brought them to Hoshido where she eventually married the Hoshidan King, Sumeragi. Corrin was officially adopted into the family, but the fact that they were not related to the Hoshidan royal family by blood was kept a secret by Sumeragi, Mikoto, and Ryoma. As a result, Corrin also never learns that Anankos is their birth father, nor do they learn that Lilith is their 'sister' due to separate vows of secrecy that Lilith and Mikoto made with Anankos' heart. Corrin is marked by their kindhearted disposition, one that leads them to put immediate trust in others one they have earned it from them. Despite their harsh, isolated upbringing in the Northern Fortress, in which Gunther notes they were rather withdrawn and hesitant during their earliest days there, Corrin was well loved and cared for by their retainers and especially by the Nohrian royal siblings. Likewise their benevolence drew strong loyalty from the likes of Jakob and Felicia, whom they spoke highly of, which encouraged both to be devoted servants to them. They also draw strong ties from Silas and Kaze, as their brief friendship with the former lead to him wanting to be a knight for them and the latter becoming a retainer after they absolved him of his guilt regarding their kidnapping. Their isolation makes them curious to the world as a whole and likewise socialize with the comrades they make during their journey. Like their Avatar predecessor Robin, Corrin is a well meaning listening ear for those who seek them out. Lilith also notes that they have a particular charm with animals as they were well liked by the horses at the Northern Fortress and they once nursed an injured bird.

Corrin's families are their most important bond and also their biggest crutch regardless of the path they take. The years spent with the Nohrian royal siblings remain treasured even if they side with Hoshido. Likewise, despite spending only a day in Hoshido with the Hoshidan royal siblings was enough to cast doubts on their upbringing, especially after experiencing the genuine joy and love from Mikoto reuniting with them. The ultimate conflict that erupts between the two nations places Corrin in the toughest position of having to reject one side despite still loving them dearly. Regardless of their choice, Corrin is pained by it and the constant fights against them further fills them with grief. If possible, Corrin tries to resolve any matters peacefully or at least spare their defeated siblings. Unfortunately, Corrin is forced into fights and duels that result in the deaths of some of their opposing siblings in Birthright and Conquest. Revelation is the only path which the two sides come together and is pleased to see both sides united under the same cause and serves as the means for them to save the world and still keep their families that they hold so dear. While not known by both sides, Azura is Corrin's family by blood and she becomes one of Corrin's closest confidant as they parallel the circumstance of their upbringing. Corrin's trusting nature and benevolence is shared with their mother, who took less than a day to convince them of her legitimacy and her sudden death was met with intense grief despite their short re-connection. As a parent, Corrin shows unconditional love to their children, especially Kana as, in their paralogue, they showed nothing less than righteous fury against the invaders who endangered them.

Despite their fresh start in war and as a leader, both Xander and Ryoma note that Corrin has surprising potential and they have faith that Corrin is the linchpin in shaping the future. In return, Corrin admires both of them, especially Xander as he was one of Corrin's instructors. Corrin frequently goes to them when seeking wise counsel. Corrin is frequently tested in all three routes, often having doubts of their qualifications. Even their indisputable, near blind trust in their comrades, while slightly admonished by both Xander and Ryoma, is also acknowledged by both to be the main reason why Corrin is a capable leader, especially for their combined forces in Revelation. At times, others have assumed that their trusting nature makes them gullible, but Corrin is far more astute than they let on and has taken advantage of this assumption. Corrin is not immune to anger and hatred as they despise Hans and Iago for their deeds during the conflict no matter which path they take and witnessing the atrocities of the war draws their ire towards Garon himself, though they do not let those feelings towards him cloud their feelings towards their adoptive siblings.

Corrin has shown a wide variety of talents and interests: they are a great piano player, enjoy writing poetry and reading about philosophy. They have trouble with household basics as they were constantly pampered by their retainers, which caused them to lack such skills, though the show great interest in at least learning how to do some basics like laundry and making tea. Overall Corrin has a good enough academic background to pass knowledge onto those less literate such as Mozu. They are also extremely observant and use creativity like asking Zola to use his powers to change Azura's appearance fool King Garon in Birthright; forcing Kotaro to reveal his kidnapping of Kagero in Conquest; and deducing a traitor in their army with little to no information in Revelation. Corrin is also shown to have a tendency to oversleep unintentionally. They are considered the one with the most hidden potential in the army. She's also a peppy and feisty at times. Due to the circumstances of the Vallite curse, Corrin struggles to unify the Hoshidan and Nohrian forces to combat the true antagonist of the events of Fates. Despite not being able to outwardly reveal their intentions, their trusting nature will shine much more than in the other two routes, leading every ally into joining their cause even though they do not fully understand the situation Corrin is facing. This has enabled more forgiving, if not kinder, characters to trust Corrin, as they have either seen their kind-hearted nature knowing that they aren't traitors (e.g. Rinkah and Kaze), they can see that they are desperately asking for trust (e.g. Sakura and Ryoma) or through other means of proof that they mean well and are telling the truth (e.g. Leo and Xander). At the end of the route, they are no longer naïve to any deceiving events happening around them (e.g. Mikoto and Gunter) and are more confident in themselves. He is relaxed and calm most of the time.