To easily sum up Ricardo... Card Captors (Sakura) + Kamen Rider Blade + hints of SAO and Kamen Rider Drive = Ricardo.

To sum him up more generally, Ricardo is a swordsman who utilizes a futuristic weapon able to scan cards and allow him to tap into their property. He's tasked with sealing monsters known as Cards Against Humanity, but finds that they were the creation of the very person who runs his army. So he's on the run.