Sanji is a young ninja in training in the Hayabusa village. He looks up to Ryu Hayabusa with great admiration and aspires to be like him someday. He also shares a special bond with Momiji and looks up to her as an older sister. Sanji's parents were murdered by Doku during his raid of the Hayabusa village at the beginning of Ninja Gaiden after the Dark Dragon Blade was stolen from the village.
He makes his next appearance in Ninja Gaiden Sigma 2 where he attempts to defend the village from another attack this time by the Tengu Brothers. Although he makes a valiant attempt he is kidnapped and Momiji persues the Tengus in an attempt to free Sanji from captivity.
In Ninja Gaiden 3 Sanji makes an appearance after finding Ryu Hayabusa unconscious within the proximity of the village. The player can later find Sanji in the village where a brief QTE event happens with him. A trophy and achievement are tied to successfully completing this QTE with Sanji.