Chrom and Sumia are both members of the Shepards. Sumia is first introduced in Chapter 2 when Lissa brings Robin to the Shepherds barracks. When she approaches Chrom she promptly trips, leaving her embarrassed. While the Shepards plan to march to Ferox, Sumia worries that she's ready for a battle yet, so Chrom tells Sumia to stay behind and watch and learn.
After defeating the Risen at Northroad, Chrom finds a wild pegasus who only settles once Sumia appears to calm them. Later, at The Longfort, Sumia rides the pegasus and saves Chrom from being hit by multiple Javelins. Robin becomes inspired by Chrom and Sumia riding together to create the Pair Up strategy.
When Chrom is beside himself with worry over Emmeryn's meeting in Plegia, Sumia tries to snap him out of it. Remembering advice from Philia, Sumia punches Chrom in the face. While the hit manages to snap Chrom back to his senses, Chrom is left slightly dazed. Lissa reveals to Sumia that normally people slap people in the face to snap people out, much to Sumia's embarrassment.
Should Chrom marry Sumia at the end of Chapter 11, Sumia becomes the new Queen of Ylisse, giving birth to Lucina two years afterwards and Cynthia shortly after that.
Sumia and Chrom share many traits in common. They can both be clumsy; while Sumia is notoriously clumsy, Chrom tripped over a pebble in their c-support. In their supports, Sumia bakes him rhubarb-and-fiddlehead pie.
Chrom and Sumia is generally accepted as the canon ship since they are shown with a child in the opening animation. Additionally, if Chrom is not married after defeating Gangrel, he will automatically marry. If all of his possible love interests have the same amount of affection, Sumia will be the first one he marries as long as she is not otherwise married. However, despite the cutscenes they share together, Chrobin is still a more popular ship.
On AO3 it is the second most written ship for Chrom and the most written for Sumia It is the sixth most written ship in the Fire Emblem: Awakening tag.
- If they are married, their daughters will be Cynthia and Lucina
- Sumia calls him "Captain" since he is the leader of the Shepards
- Sumia and Chrom as a pair could be a reference to Marth and Caeda, as Marth is the blue haired Lord whom Chrom is descendant from and Sumia is a pegasus knight like Caeda