The Touryou (頭領: Chieftain) of the Arashikage Clan, Sen Arashikage is the grandmother of Tomisaburo and Kenta. After Kenta became a Nuke-Nin (抜け忍 renegade ninja) and joined with Cobra, she decided Tomisaburo would be next in line to lead, and had him study under the ways of their shinobi ancestors.
After escaping Kenta, Snake Eyes is brought to meet Sen after he saves Tommy’s life. Sen agrees to her grandson’s request and allows Snake Eyes to take the Three Challenges of the Warrior to determine if he is a worthy applicant to join the clan. As the matriarch of the Arashikage Clan, Sen oversees Snake Eyes as he completes the challenges. When Snake Eyes fails the third test she scolds Akiko for helping save his life and her grandson for inviting Snake Eyes into the clan. Sen orders the Blind Master to use his abilities of perception to determine snake eyes motives and then she decides to let him live after it is determined that he was being truthful. But tells him he is not to be of Arashikage.
The clan matriarch once again scolds Tommy and Akiko after she learns that the Jewel of the Sun was stolen by Snake Eyes. She chooses to fight alongside her clan when the castle is attacked by Kenta and Corba, even though the Blind Master insists that she get to safety. After Kenta betrays Cobra and the Baronness, she sees that Snake Eyes had returned. She is grateful for his assistance, but warns that she herself will end him if he betrays the clan again. After the battle is complete She decides that she cannot allow her grandson Tommy to succeed her as the leader of the clan since he broke the clan's oath to never use the Jewel of the Sun, only defend it. As she and the masters watch Tomisaburo storm out of the castle enraged and betrayed, Sen tries to comfort her grandson, telling him he is forever loved as her grandson and member of the family, but her feelings fall on deaf ears, as Tommy abandons the ancestral ring, signifying his abandonment of the Clan and the Arashikage family, leaving Sen to weep silently, knowing her grandson is headed down a treacherous path.