The daughter of Sumia from the future. If Chrom marries Sumia then Cynthia will be the sister of Lucina, if Sumia marries the Avatar then she will be Morgan's sister. Otherwise she will be an only child.

In the past she used to be a "girly-girl" according to her conversation with Severa in the Harvest Scramble. Cynthia grew up with the stories of the "Generation of Heroes" or the stories of her parents and their friends, even if they were not all entirely accurate. Cynthia spent time with Sumia often and the two begun planning on making a spear together and Cynthia managed to make the spearhead. Unfortunately Sumia was killed in battle before this project could start. Sumia's pegasus eventually found its way back home and wanted to protect Cynthia, thus becoming her mount. She also received Sumia's wedding ring and has worn it ever since. Sumia's death weighed heavily on her and because of the stories of her parents, Cynthia changed her entire personality and begun hanging out with boys more than she did with girls. She eventually began training to be a hero and to become a member of the Pegasus Knight Squad. Cynthia would later join Lucina and the other children on their journey to go to the past and prevent the ruinous future. After arriving in the current timeline, Cynthia searched for Chrom's army. On the way she bumped into a man claiming to be Chrom and instantly believed him despite the lack of resemblance. She began to follow his orders and aided him as much as she could.