In this game, Kieran serves as a member of Crimea's 5th Platoon, who, alongside Geoffrey, is entrusted with the honorable duty of escorting Elincia, Crimea's secret princess, from the Daein attack on Melior during the Mad King's War. When the escort is later ambushed by Daein forces, he is captured by the Daein army and held in Castle Canteus. Kieran is later rescued by Ike's forces, whereupon he will remain with them until the game reaches its conclusion. He will then cede his services back to Crimea, serving under the newly-crowned Queen Elincia.
Kieran is first introduced in this game in a Base Conversation in Chapter 2-3, where he is given a Silver Axe as a gift from Geoffrey himself. Alongside the other Crimean Royal Knights, Kieran will then lay siege to Castle Felirae, essentially falling into Ludveck's trap. The Royal Knights will then rush to Fort Alpea in the next preceding chapter, serving as reinforcements to Elincia's stranded forces.
Kieran later appears as an enemy unit in Chapter 3-12 to the Daein army, representing the Crimean Royal Knights in Geoffrey's absence. The chances of the player managing to engage him in battle, however, are very slim if Jill is not used to fly down the cliff.