The Wano Country arc in One Piece delivers one of its most unexpected twists when Big Mom suddenly loses her memory and begins helping Monkey D. Luffy. Known as one of the Four Emperors, Big Mom is typically portrayed as a terrifying and unpredictable force, making her temporary shift in behavior both shocking and confusing for viewers.
This moment happens after Big Mom arrives in Wano while chasing the Straw Hats, only to suffer an accident that completely alters her personality. Instead of her usual ruthless self, she becomes gentle, kind, and even protective of others. This leads to her forming a bond with characters like Tama and indirectly assisting Luffy’s cause. To understand why this happens, it is important to break down the cause of her amnesia, how it affects her personality, and why she ends up helping Luffy despite being one of his biggest enemies.
How Big Mom Lost Her Memory in Wano
Big Mom’s memory loss occurs shortly after she reaches Wano in pursuit of the Straw Hats. While trying to climb the waterfall leading into the country, her ship is attacked and she falls into the sea. Since she is a Devil Fruit user, she cannot swim, which leaves her unconscious and vulnerable. She eventually washes ashore at Kuri, where she is found by locals with no recollection of who she is.
This incident is portrayed as a form of trauma-induced amnesia. The fall and impact, combined with near drowning, likely caused temporary memory loss. In the world of One Piece, while not deeply scientific, such physical trauma has been shown to affect characters’ mental states in similar ways. Big Mom awakening without her memories sets the stage for a completely different version of her personality to emerge.
Once Big Mom loses her memories, she adopts a much calmer and kinder personality. Without her past experiences, ambitions, and obsessions, her core traits shift dramatically. She no longer identifies as a Yonko or pirate captain, and instead behaves more like a naive and good-hearted individual.
Her bond with Tama plays a key role in this transformation. Tama feeds her and treats her with kindness, which Big Mom reciprocates. This leads to her taking on the nickname “O-Lin” and acting as a protective figure rather than a threat. The absence of her traumatic past and hunger-driven impulses allows her more innocent nature to surface.
This also connects to her childhood backstory. Even before becoming a pirate, Big Mom displayed both kindness and destructive tendencies. Her amnesia essentially resets her personality closer to that early, less corrupted state, removing the influence of years of power and conflict.
How Big Mom Ends Up Helping Luffy
Big Mom does not intentionally decide to help Luffy. Instead, her actions indirectly benefit him due to her altered personality and circumstances. While traveling with Tama and others, she ends up opposing Kaido’s forces, which aligns her temporarily with Luffy’s allies.
One of the most important moments comes when she reaches Udon Prison. There, she disrupts the control of Kaido’s subordinates and creates chaos that ultimately helps Luffy progress in his training and regain strength. Her presence alone shifts the balance of power, making it easier for Luffy and his allies to take control of the situation.
Even though she is not directly fighting for Luffy, her actions weaken Kaido’s hold over Wano. This makes her an accidental ally, showcasing how unpredictable events in One Piece can completely change the course of a battle.
Big Mom’s amnesia is only temporary. After another head injury during her time in Udon, her memories return, and she immediately reverts to her original personality. Once she remembers who she is, her hostility toward Luffy and others returns as well.
However, by this point, the damage to Kaido’s forces has already been done. Luffy has gained valuable time and progress thanks to the chaos she caused. This ensures that even though Big Mom is no longer helping, her brief period of amnesia has a lasting impact on the story.
Her return to full strength and awareness also raises the stakes of the Wano arc. Instead of removing her as a threat, the story uses her amnesia as a temporary twist that ultimately makes the conflict even more intense.