Kris

My Unit is a custom character created by the player who participates in the game's stories and battles, similar to the Tactician from Fire Emblem: Rekka no Ken. My Unit is a youth of Altea who joins the Altean Knights one year after the end of Fire Emblem: Shadow Dragon along with Katarina. The prologue of Shin Monshō no Nazo covers My Unit's rise from a rookie knight to one of Marth's personal guard. By the end of the prologue, they are a member of the 7th platoon of Altean Knights. Their eventual fate is to become the "Hero of Shadow", Marth's confidant and friend who holds no record in history. This unit joins the 7th platoon, along with Rody, Ruke and Katarina.

Players can change My Unit's name, gender, starting class, appearance and background. They can choose what their characters historic background, past present and future, which is thought to influence their base stats and stat growths. The default appearance of My Unit is the blue-haired, male Mercenary who stands next to Marth in the game's boxart. The default female My Unit also has blue hair and is a Myrmidon.

Classes
Classes available for males only are Fighter, Knight, and Mercenary. The female only classes are Myrmidon and Pegasus Knight. Classes available for both genders are Archer, Mage and Cavalier.