The "Sky of the Night Light", Noctis is the last Heir of the Caelum Dynasty and protects his city-state from those who seek the Crystals. The Crystals allow him to control his weapon by telekinesis, as they range from swords, to spears, to lances. He is said to be the first to break the mold of typical Final Fantasy protagonists' personalities, as he is idiosyncratic.
Beautiful cosplay! I've actually yet to play this game, or any of the Final Fantasy games for that matter, but I've always appreciated their art work. And it looks like the cosplayer put a lot of effort in the details of his sword too. Great job!
EDIT: Thanks to Xan for letting me know the cosplayer is Rainer Tachibana from Singapore!