I spent years inside Kainé's body. Tormenting her from within. I felt her pain, her emotions as if they were my own. And there was so much pain... So when I say she's free now. I want you to believe me. Thanks to you, Kainé has been forgiven. And saved.
-Tyrann to NieR, Ending D
Tyrann, Kainé's shade parts reveal his backstory when Kainé's Dreams are unlocked during the second playthrough. Her dream, "Encounter" features how he crept up as a voice to her while she was dying and mutilated. He wanted to take her body but surprisingly managed to merge into her missing parts instead even as she was resisting.
Tyrann manages to lure her into succumbing to his possession by tempting her with his Shade powers. His powers would soon also belong to her and she can get the vengeance she needed for the death of her grandmother, Kali. He does not care if it meant killing other Shades. She accepts his abilities and lives on with Tyrann in his heart.
During the second playthrough, Tyrann's voice will be more apparent throughout the game. His excitement for killing will be expressed during combat. In all the years living with her, Tyrann's attachment to Kainé will also start to show, especially seen in Endings C & D.
In one of the final Endings, Kainé's Shade takes over and commences a boss battle sequence with NieR, at her defeat, Tyrann tries to help Kainé and offers NieR two options:
- Plunge his sword into her chest and set her free (Ending C)
- Make her a human being again by trading NieRs own existence with hers (Ending D)
The choice is up to the player which will determine the ending.
Tyrann to Kainé as he possesses her
- "So listen, my name's Tyrann. And if you ever need me, I'll
just be hanging out in this piece of meat you call a heart.
Now get to it! The more you kill, the more your heart turns
rotten and sour... and I like rotten and sour!"