In summary, Full Dive RPG follows the life of ex-runner Hiro. After wetting himself during a pivotal race, he locks himself away in his room and becomes a hikikomori. A hikikomori is a person who stays inside and avoids social contact with others whenever possible. They often shun education and even their jobs in severe cases to focus on more important things (like gaming and anime). There is a stigma placed on hikikomori (in that they are dirty, have poor social skills, etc) and Full Dive RPG explores this nicely.

Hiro was very popular as a runner. He held the adoration of his idols, his sister, and even his many friends. However, after losing his big race, his dormant anger erupted and caused him to alienate many of his friends. It is not until Hiro starts playing a new VR game known as Kiwame Quest (that he was coaxed into buying by a busty saleswoman) that his life starts to get back on track. KQ is a "shitty game". The game mirrors real-world attributes and so those unfit in real life, cannot hope to defeat the many challenges in the game. Yet, despite the game being as shitty as it is, Hiro returns time and again in hopes to one day beat KQ in its entirety.

Full Dive RPG, on the surface, is a light-hearted comedy anime about an interesting concept. What would you do if you were dropped into a game world where the NPCs are presented exactly the same as humans in our time? You'd probably stop playing, right? Well, that's exactly what happened to KQ. People stopped playing and the game lost a majority of its player base. However, for people like Hiro, there is no alternative. There is no real world to escape to when your life revolves around playing games. This results in Hiro reluctantly suffering through KQ alongside Reona.

The more Hiro plays KQ the more he comes to enjoy it. He enjoys working towards something even if that something is all a part of some game. He enjoys spending time with Reona and the other realistic NPCs, even shedding tears when some of them die. He trains his body in the real world and rediscovers his passion for running. Full Dive RPG wants to show its audience the dangers of addiction and the importance of social interaction. Even if it's through a game with friends you only know on the internet, it's important to put yourself out there and meet people, make friends and enjoy life with people you care about. In the final episode, we see a fire burning in Hiro both to achieve his in-game goals as well as to better himself in the real world (both physically and his lashing out against his sister and Reona).