- Main article: Mutual Enemies/Script
Corrin calls his/her army to stop their advance upon arriving in Mokushu and seeing a smoke signal from the forest; Kaze states that it's Saizo's signal stating that he's engaging a large number of enemy troops; Corrin proposes that they help, but Kaze states that the signal Saizo is sending is intended to ward allies away from a dangerous spot and suggests traveling elsewhere. Corrin states that he/she has made up his/her mind, that they're going to help Saizo, and calls the army into action; Kaze questions Corrin's motives, to which Corrin states that they need to gather allies or else they can't fight the mutual enemy of Hoshido and Nohr, and he/she won't ignore any chance to gather such an ally, to which Kaze relents.
Deeper into the forest, Corrin notes it as being the origin of Saizo's smoke signal and wonders if he's still in the area, to which Azura states that the Mokushu forest makes things difficult to tell and that it's easy to get lost in the area; as Azura spots footprints, she suggests that they follow them, with Takumi having to console Sakura during the advance. Kaze spots an attack launching toward Takumi and warns him, then defends him from the strike; Takumi notes the weapon used as being a shuriken, with Kaze stating that they're the kind the Mokushujin fighters use. Takumi deduces that the Mokushujin are preparing an attack, to which Kaze notes that the shuriken launched at them was launched by a scout and thus more enemies are heading their way; Corrin takes the opportunity to call the army into battle. Preparations take place at this point.
Once preparation are finished, we witness the daimyo of Mokushu, Kotaro, telling his hostage, Kagero, that Corrin's army has walked right into his trap in the same fashion Kagero did; Kagero insults Kotaro's ninja skills and asks why he took her hostage given Mokushu is allied with Hoshido, to which Kotaro states he bears bad news--he has decided to ally with Garon, the Nohrian king, and has been waiting for an opportunity to do so for a long time, with Mokushu rising up to replace a fallen Hoshido and himself as its king. Kagero questions Kotaro's sanity, to which Kotaro states that he needs to keep Kagero alive for now but that could change at any time and has one of his ninjas take her away; Kagero states that she has always been prepared to die carrying out her mission, but regrets failing to deliver Ryoma's message. We cut over to Saizo's group, where he asks Orochi if this is the area where Kagero was captured, to which Orochi states that this appears to be the area their scout described but she can't be sure since they're deep into the woods; Saizo suggests that the group search the area, to which Reina notes the animosity within the forest and suggests that she handle the enemies within, after which Saizo tells Reina that she needs to stay focused. Back over to Corrin's group, Corrin states that he/she has spotted Saizo, after which Azura notes that Saizo appears to be fighting the same enemies they are, and that he may be more willing to join now than back at their previous encounter; the battle begins at this point.
Should Corrin speak with Saizo, Saizo questions Corrin's motives in following the smoke signal, to which Corrin states that he/she wouldn't simply abandom him to the enemy; Saizo states that no traitor would risk themselves to help him and decides to join Corrin's cause, then reveals Kagero's plight. The player may now control Saizo, Orochi, and Reina at this point.
Once the battle ends, Corrin states that they've taken care of the Mokushujin and asks where Kagero is, to which Sakura states that she's located her; Kagero asks what Corrin's doing in the area, given that she last heard that he/she had betrayed Ryoma and fled the battlefield; Sakura states that Corrin hasn't betrayed anyone and that herself and Takumi travelling with him/her is proof, to which Kagero asks Corrin for forgiveness and Corrin stating he/she is glad Kagero's safe. Saizo and Kagero then check up on one another, after which Kagero reveals that Ryoma was on his way to Cheve near the Nohrian border; Kagero reveals that the Chevois are currently fighting Nohrian forces, with Ryoma seeking to take advantage of the situation and use them to infiltrate Nohr. Takumi suggests to Corrin that they head for the nearest port, as they'll need a boat in order to reach Cheve; Corrin suggests that the group hurry, as they're going to need Ryoma's help, then suggests that Ryoma might know about the dragon Izana spoke of with his dying breath.
Summary
Corrin rescues Archduke Izana from a Nohrian illusionist and gains a valuable ally, Takumi. The group then heads into a forest to rescue more Hoshidan forces.