The story follows a similar plot to the anime but is slightly different to add in new characters.
The story begins with the Protagonist transferring to Access Academy High School and moving into a dorm in the city. After seeing how popular the virtual stadium game Armored Arena was, the Protagonist decides to find out more about the game and talks to a girl obsessed with the game named Haruhi Asakura and is forced join by her. Now an official player, the Protagonist is given his/her own armor and is forced to play his/her first match after accidently bumping into Aruka Kamijou, the school bully. After the match, the Protagonist meets with Haruhi's childhood friend, Yuuto Ueda, a new but highly skilled Arena player. As the story goes on, the Protagonist has to deal with an organization known as Globe and needs to defeat them to save the world.
Armored Arena is a virtual battle stadium game which could allow players to battle each other from all over the world or locally in the Arena. Players are able to play if they have an Armored Card, it is the item that gives the player their armor and allows them to transfer their minds into the game. Every player's armor is generated using their personality and then uses the computer to create the best design, abilities, and skills for the player. Players could practice and gain new skills and abilities in the Training Arena, but though skills are not limited, abilities must be limited to only two unless an Ability Card is used.
In the beginning of the game, the player can create their character by choosing a gender, voice, face, hair, body type, and name. The name of the Protagonist can be chosen from a list, which will be said when someone talks in the game; the name could also be customized to the player's choosing, but it won't be spoken in the game. The Armor Abilities and Class are available for choosing and customizing after joining the Armored Arena.
Combining elements of traditional console role-playing games and simulation games, the gameplay of Armored Arena: Advent -A- involves following the life of the game's protagonist, as he/she attends school and works to build relationships with other people. Outside of key events, the protagonist attends school, and can interact with other students and characters, spend time at part-time jobs to earn money, or engage in other activities by free roaming in the city, similar to the Shin Megami Tensei: Persona games. The relationships with the other characters and victories of Arena matches will determine the ending of the game. There are four different endings, Champion (win all matches), Popular (befriend most unique characters), Famous (win all matches and befriend most unique characters), and Average.
During battle gameplay, the player controls the Protagonist in a third-person shooter or beat 'em up depending on the Armor Class of the Protagonist. There are six different Armor Classes, each with their own different abilities and play style. Each Armor Class has their own Abilities, which can be activated in the battle palette on the bottom of the screen. The character's life bar is displayed on the top left of the screen along with the stamina bar, the match will be lost if the Protagonist runs out of life, however, the stamina bar will only slow down and disable the use of the Abilities for a certain amount of time. The character can find healing items throughout the map to recover a certain amount of life. The character is also allowed to free roam anywhere in the Arena during a match as long as he/she doesn't leave the field, leaving the field for 10 seconds will be an automatic loss. During team matches, the character could give commands to the other characters in the match, but they will not always respond.
There is a multiplayer mode where players could play online or locally with other players using their created characters from their profiles in the Armored Arena. There are four profiles available to use before starting the game. In local multiplayer, the players could choose between one of the characters from one of the profiles or choose a basic randomized Armor Class and battle in four different game modes. In online multiplayer, the player must choose their character from their profile and could battle with up to 16 other players in seven game modes.
There are four game modes for local multiplayer and seven for online. The local game modes are:
- All players fight each other until all other players are out of life.
- Team Battle
- Players team up with each other to fight the other players until they run out of life.
- All players fight each other until the score or time limit is reached.
- Team Collector
- Players team up with each other to fight the other players until the score or time limit is reached.
The other three game modes are:
- Mixed Team Battle
- Players team up with each other to fight the other three teams until they run out of life.
- Players team up to defeat the Juggernaut, the person with the highest score wins. The Juggernaut is chosen at random in the start of the match but who ever defeats the Juggernaut becomes it until he/she runs out of life.
- Target & Eliminate
- All players search for their wanted target and eliminate him/her. The player with the highest score in the end wins.
Armored Arena Classes
Armor Classes are the types of armor that the players wear for battle. Each Armor Class is automatically selected during the process of the armor creation and cannot be changed (except in Yuuto and the Protagonist's case, which is an ability and not a permanent change).
- Fighter - The most balanced Armor Class. It can use light or heavy melee weapons such as knuckles or axes, but mainly swords. It's abilities are Courage, Hunt, Recharge, and Struggle.
- Runner - The fastest Armor Class. It can only use light weapons such as magnums or dual swords. It's abilities are Teleport, Acceleration, Afterimage, and Boost.
- Striker - A balanced fast and powerful Armor Class. It can use heavy or light melee or ranged weapons such as rocket launchers or axes, but choosing a heavy or light weapon changes the speed and power. It's abilities are Pause, Flight, Smash, and Clone.
- Ranger - The Armor Class that requires the most skill to master. It can use any ranged weapons such as a rocket launcher or magnum. It's abilities are Map, Navigate, Capture, and Camo.
- Tank - The most powerful Armor Class. It can only use heavy melee weapons such as axes or hammers, the only light weapons it can use are knuckles. It's abilities are Protection, Quake, Twister, and Blast.
- Changer - The only Armor Class with the ability to change it's class and have no armor of its own. It can use any of the weapons and change them at anytime. Like the weapons, the abilities can change at anytime depending on the Armor Class, but it really has only one true ability, Switch. The only player to have this class is Yuuto and the Protagonist. This class will not be allowed in multiplayer modes.
The abilities are the primary skills of the Armor Classes and are usually the deciding factors of a match, which is why the abilities are limited to only two per player and had limiters on the abilities.
- Courage - A Fighter Class ability. This ability temperarly rises the power of the Fighter by half.
- Hunt - A Fighter Class ability. This ability rises the sense of the Fighter, giving them a better chance of noticing the other player(s).
- Recharge - A Fighter Class ability. This ability gives the Fighter the power to energize itself when the energy is low and unable to use skills.
- Struggle - A Fighter Class ability. This ability automatically activates when the Fighter is low in health, giving them a power and speed boost.
- Teleport - A Runner Class ability. This ability gives the Runner the power to teleport anywhere in the map within their limit.
- Acceleration - A Runner Class ability. This ability lets the Runner have a fast starting dash, increasing the speed of the Runner.
- Afterimage - A Runner Class ability. This ability allows the Runner to leave behind clones of themselves to be used as decoys.
- Boost - A Runner Class ability. This ability temperarly increases the Runner's speed by half.
- Pause - A Striker Class ability. This ability allows the Striker to temperarly stop time in the Arena.
- Flight - A Striker Class ability. This ability gives the Striker the power to fly.
- Smash - A Striker Class ability. This ability gives the Striker a quick speed and strength power up for one attack or dash per match.
- Clone - A Striker Class ability. This ability creates a clone of the Striker to double the attack power. The clone will disappear when hit or when the Striker runs out of energy.
- Map - A Ranger Class ability. This ability creates a map of the entire Arena, showing the Ranger's current position in the map.
- Navigate - A Ranger Class ability. This ability shows a path for the Ranger to get somewhere quickly.
- Capture - A Ranger Class ability. This ability allows the Ranger to set traps and temperarly capture an opponent.
- Camo - A Ranger Class ability. This ability lets the Ranger become invisible and undetected by radars for as long as the energy remains.
- Protection - A Tank Class ability. This ability creates an invincible shield for the Tank until the energy runs out.
- Quake - A Tank Class ability. This ability allows the Tank to be able to create an earthquake by hitting the ground using its energy.
- Twister - A Tank Class ability. This ability allows the Tank to be able to create a tornado using its energy.
- Blast - A Tank Class ability. This ability allows the Tank to shoot energy beams out of its hands.
- Switch - A Changer Class ability. This ability allows the Changer to switch into any other Armor Class and also change the abilities and weapons as well.
Skills are like abilities except weaker and takes energy. The amount of skills a player can hold depends on how the powerful player is. The skills are not locked for any class, every skill can be used by any Armor Class as long as the player is able to use it.