Assassin's Creed Shadows: How to complete Brothers in Arms main quest

The Brothers in Arms main quest in Assassin's Creed Shadows is the 48th mission, unlocking after completing Astray. This time, the story takes Yasuke (or Naoe) into a brutal fight against The Ox’s forces, helping a fugitive ronin named Koshiro track down his former comrade, Commander Seiji. You can expect intense sword combat and a choice that will determine Seiji’s fate.

Here's everything you need to know to complete the Brothers in Arms main quest in Assassin's Creed Shadows.

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Brothers in Arms main quest walkthrough in Assassin's Creed Shadows

Brothers in Arms main quest's whereabouts and objectives in Assassin's Creed Shadows (Image via Sportskeeda Gaming || Ubisoft)

Find Koshiro and help him

This mission kicks off northwest of Miko Docks, where Koshiro is fighting off attackers. You must get there quickly because he’s outnumbered. Jump into the fight and help him defeat the enemies before speaking with him.

Assisting Koshiro (Image via Sportskeeda Gaming || Ubisoft)

Koshiro reveals that he’s searching for Commander Seiji, a former comrade who’s still serving The Ox. His location automatically appears on your map, making it easy to track him down.

Read also — All Lost Page locations of Byodoin Temple in Assassin's Creed Shadows

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Head to Kanki Castle

Activate the Pathfinder option and mount your horse, proceeding west on your journey toward Kanki Castle. The quickest approach is from the north end, where you should be next to Jorakuji Temple. As Naoe, use the grappling hook to gain access without alerting guards. Yasuke will have to approach through the front entrance; this forces its user to fight through the guards.

Once you enter, use Observe to find Seiji. He's identified by a blue dot, but an old bug can sometimes duplicate markers. Don't mind the extras — the actual Commander Seiji is the one that's farthest west. His name will pop up above him when you approach.

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Fight Commander Seiji

Taking down Commander Seiji (Image via Sportskeeda Gaming || Ubisoft)

By the time you get to him, Koshiro is already busy fighting Seiji. This puts you at an advantage — it's a 2v1 battle, so this is one of the simpler boss fights. If you play as Naoe, you can backstab Seiji and avoid fighting him altogether. Otherwise, fight him with swords and take him out with swift counterattacks.

Taking Seiji into the shadows (Image via Sportskeeda Gaming || Ubisoft)

Once he’s defeated, you’ll get a final choice:

• Kill the commander
• Spare the commander

It's a cosmetic choice only — whether you allow him to escape or kill him, the narrative is the same.

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Mission completion and rewards

Finishing Brothers in Arms grants 1000 EXP, bringing you one step closer to toppling The Ox and advancing deeper into Assassin’s Creed Shadows.

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