Kingsglaive: FFXV Fan Kansha Tokubetsu Movie

Both and essentially short animated promotions for the FF XV game, although the Kingsglaive ONA is also promoting the prequel movie "Kingsglaive: Final Fantasy XV" and the Episode Ardyn Prologue is promotion for specific DLC for the game. They still target the same demographic and fans of the game will find some enjoyment in both. 

Both promotional ONA's set in the same canon/universe, the world of Final Fantasy XV. Both promote the game and intend to drive up hype/attention towards the series, the Fan Kansha Tokubetsu Movie is also promoting XV's prequel movie Kingsglaive.