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Remus Lupin stared in awe and melancholy as 13 year old Harry cast his first successful corporeal Patronus. He seemed as adept at magic as James and Lily, if not more.

The worst - his Patronus was a stag - James's animagus form. Remus could not look away as much as he wanted to. He could not help but think of James during their third year, when he had the same expression on his face as Harry did now, and produced a corporeal Patronus for the first time, because the marauders had decided to learn the charm earlier than everyone else, and a stag had burst out of the tip of his wand. He could not help but think of James in their fifth year, when after continuous hard work of so many years, they were finally able to transform into animals - and James had turned into a beautiful stag.

Remus wanted to hold Harry tight, to tell him how much he loved him, to tell him how much Harry had loved him too, how much he reminds him of James, what James had meant to him. But he didn't. Harry needed Professor Lupin, not Uncle Moony.