|Debut||Ninja Gaiden: Dragon Sword|
|Japanese Voice||Rika Komatsu|
|English Voice||Tara Strong (Ninja Gaiden Sigma 2)|
Wendee Lee (Ninja Gaiden 3)
Sanji (サンジ) is a young Ninja in training of the Hayabusa Ninja Clan. Like the other kids in the village, he looks up to Ryu and aspires to be a Master Ninja just like him. He also sees Momiji as an older sister.
Ninja Gaiden: Dragon Sword
Sanji is one of the surviving members of the Hayabusa Clan. His parents were murdered by Doku during the Dark Dragon Blade Incident. Although he's young, he has shown great potential as a Ninja. He looks up to Ryu, and hopes to someday be a true Ninja like him.
Ninja Gaiden Sigma 2
The Black Spider Ninjas have attacked the village once again and Sanji is defeated by one of the elder of the Tengu Brothers and kidnapped, sparking Momiji's attempt to save him.
Ninja Gaiden 3: Razor's Edge
When Ryu returns to the village, Sanji finds him unconscious and brings him to Momiji. Wanting to be a better ninja, Sanji requests for Ryu to train with him someday, which his master happily agrees.
- Sanji carries the Double Sword Guard Charm as a keepsake of his late father. His father was a first rate ninja and master of the twin-sword technique, who died during the Dark Dragon Blade incident.
- Sanji wishes to master the techniques of his father with all his heart.
- Sanji carries the Double Sword Guard Charms with him wherever he goes, along with a pair of sword which he is not quite ready to use yet.
- In Ninja Gaiden Sigma 2, Sanji drops the Double Sword Guard Charm in the Hayabusa village when he is captured by one of the Tengu Brothers. Momiji finds the charm which prompts her to search for Sanji.
- When playing as Momiji in Ninja Gaiden Sigma 2 in the chapter "The Shrine Maiden's Battle", you can find the Double Sword Guard Charm in your inventory and check its details.
- Sanji in the first two games would likely be ten years old. In NG3 he would've been 12 years old (since DOA5 took place two years after DOA4, NG1, and NG2.