Leon arrived the Tower in the Last City, feeling his body aching from the long mission in the Cosmodrome after hunting down a gang of Fallen that was collecting technology from the Golden Era. While he walks to Zavala to let him know he’s back, he can see the commander talking with a little guardian he never saw before.

It must be a newborn Thinks Leon, watching the new one walking away, while she talks with her Ghost, maybe he can talk with her later.