This is a First Person Camera mod for Assassin's Creed Unity, and it has a download link.
The camera follows Arno's animated head, hides the head & hood from the main view while preserving cast shadows, and automatically pulls back when the camera approaches geometry. It is designed for immersive walking, parkour, combat, and exploration.
The mod author has said it's not nearly complete. It's still decently polished for what it is, and it reminds me of Dying Light 2. I hope he continues to polish and smoothen this out.