"I'll be your Navi, Immelman."
Claus would never forget those words. Before Dio, a Navi had been someone to help him fly his Vanship, and while Lavie had a special place in his heart- they grew up together, after all- he felt that he had never truly understood what a Navi was. Neither, Claus liked to recall, did Tatiana, although he was fairly sure Alister was aware of the gap between her actual role and what she should have been doing.
Without a Pilot and a Navi, a Vanship could not function, but even those two things would not make it fly well. To truly fly at the limit of one's potential, one needed intimate knowledge of both the ship and one's co-pilot. Claus had thought he had had that with Lavie due to their shared past and goal to reach the Grand Stream, but the Silverna had broken that misconception quickly. Then it had shown Claus that sometimes such synchronicity could be found with someone you otherwise had nothing in common with.
Within a few days of Dio's arrival, Claus was already accustomed to the feel of slim arms circling him from behind, warmth soaking into his back. It was slightly shocking when warm lips first pressed against the skin of his neck, but he soon became accustomed to that as well. After that, Claus found himself noticing the change in atmosphere whenever Dio entered a room, and feeling strangely out of place without the small, but frequent, touches offered by the young Principal. From there it was a natural progression.
Claus and Dio learned a new skyscape; one consisting of planes of flesh and contours of bone, whispered breezes and smoke trails of fingertips, and then a moment of glorious, mind shattering freedom, even greater than that of flying free in the skies. Then they really flew together, and Claus felt almost the same reaching, but even the small distance between the Pilot and Navi's seats was too great to recreate the sensation.
After that, though, Claus knew what a Navi was, and what a Pilot was, and that without one the other was nothing, but once brought together, they were invincible.