Jack and the Warrior Woman

A talented warrior named Ikra joins Jack as he seeks a magical jewel that could send him back to his own time and can only be used by the pure of heart. Once they reach the gem, it scans them and judges that Ikra is not pure of heart, then spawns a monster Ikra fights. After defeating the monster, she destroys the gem, revealing “herself” as Aku and derailing Jack’s quest.