Crux's entire vocabulary is made up of "kukuruyu". Periodically abused by the Lords of Gaudium, Crux developed feelings for Makenshi when he saved her life. Crux rebelled against Oscha and helped the protagonists during the battle against Chaos Tyrant.
After the battle, Crux carried Makenshi away and tended to his wounds. She later becomes his traveling companion. Crux was damaged by Crux Number-2 when she found Madoushi's grave. Crux received a gem from Makenshi's older brother Madoushi, which contains his very power, from his grave. From this Makenshi learns the mist powers of his brother, and Crux is able to transform into the Cross Sword, Makenshi's secondary weapon.