After the death of Crepus at the hands of his own delusion, Kaeya and Diluc fell off. This was because Kaeya arrived too late to the scene, which resulted in him not being able to save his adoptive father. Afterward, Kaeya revealed his true identity as a secret agent from Khaenri'ah to Diluc. This confrontation led to a fierce battle between the two brothers, and in the midst of the battle, Kaeya felt a surge of elemental energy coursing through his body. According to Kaeya's story in Vision; Friendship Lv. 6: "Bitterly cold and brittle elemental energy burst forth from the tip of his sword to meet Diluc’s searing flames head-on. The clash of crimson fire and azure ice created a sudden swirl of wind that stunned them both. This was the grim moment at which Kaeya's Vision appeared."