Momochi Sandayu first appeared when he attempted to kill Yoshiyuki-hime, or the maid posing as her, while she held audience in Wakigami castle. His attack was thwarted both by Kamimusubi, who pulled the maid to the ground, and Tsukuda Katsuo, who appeared and blocked the strike with his own weapon. Sandayu did not tarry, but rather escaped as soon as it was obvious his assassination had failed.
He later appeared in Iga province, killing several Igamono ninja and kunoichi who had surrounded Fujibayashi Nagato, very likely saving her life. Though his appearance obviously had an impact on Nagato, who recognized him and spoke his name, he simply stated that his debt was now fulfilled, and vanished.
Momochi Sandayu later showed himself at the battle of Awa, appearing from the shadows to engage Baby Huey, flanking the Oni with Chosokabe Nobuchika. When Huey was brought under Chosokabe Morichika‘s control, he disengaged immediately, slipping back into the shadows.
He reappeared after a short time near Hashinara Katamoto, stating that he could not be allowed to continue, and launching an attack that was immediately blocked by Ishikawa Goemon. Ignoring Goemon’s pleas for him to return to his senses, he defeated her with a brutal cut to the stomach which almost killed her instantly.
Raizou immediately joined the fight with Motoyama Tsugutoshi in tow, furious and aiming to avenge his master. Though he blocked both of their attacks easily, Sandayu was distracted by the assault and did not notice Amenotokotachi’s attack from the other docks, an energy blast which took him full in the side and sent him flying several feet, killing him before he hit the ground.