Ar nosurge: Ode to an Unborn Star is a Japanese role-playing video game developed by Gust and published by Koei Tecmo. Directed by Akira Tsuchiya, the game takes the anime art style of Gust's flagship Atelier video game series and puts it into a science fiction space opera-type setting. While playing as an RPG, the game is very story heavy, with virtually all gameplay mechanics feeding into the overall plot, including many segments playing as an interactive visual novel. Designed with player immersion as a core concept, the player actually plays as themselves, using their video game console as a means to communicate with characters as themselves, while otherwise controlling characters as one typically does in a video game. The game alternates between following two sets of characters - Delta and Casty, and Earthes and Ion, as they work through issues related to the hostile race known as Sharl that are antagonizing the space station that humanity currently lives on, while working through many of their own personal issues of their past.

The game debuted with a worldwide release on the PlayStation 3 across in 2014. An extended version containing all of the game's downloadable content (DLC), Ar nosurge Plus, was released worldwide the following year on the PlayStation Vita. A remastered high definition version, Ar nosurge DX, was released in Japan in March 2021 for the Nintendo Switch, PlayStation 4 and Microsoft Windows.

The game plays as a JRPG with visual novel segments. On the role-playing side, the game does not have a traditional party setup, but rather, the game alternates between two sets of characters; Delta and Cass on one side, and Ion and Earthes on the other. In the regular game field, the game plays as most JRPGs do; the player maneuver's the character through the game environment, exploring small areas to find non-player characters to interact with or items to collect to aid them through progressing the game. In certain areas, a bar is present in the corner of the screen. The bar indicates that random battles may occur in that area, and indicate how increasingly likely they are to occur as movement transpires on the map. Optional small talk between characters arises as the game world is explored as well.

The game employs a turn based battle system with timed button press elements that amplify effectiveness. Only two characters participate in a battle at the time - Delta or Earthes as the attacker/defender, and Cass or Ion who stands back to charge their "Song Magic" special move. Multiple waves of enemies approach the player, which the player takes on each wave one at a time as each is defeated, with each wave placing characters on a 3x3 grid. The player has a selection of different types of regular attacks, with varying strengths, weaknesses, and area of effects, as well as the option of using consumable items or special "Friend Skills" earned through game progression that award various effects. The better the player strings together attacks, the faster the Song Magic's meter grows, which increases its attack power. Attacks phases can be extended if enemies are hit with a "break" status incurred by good fighting, though attack number are finite, and once they are used up, the attack phase ends. The battle transitions to the enemy phase, where the player must defends through time button presses to reduce damage aimed at Cass or Ion. Battles continue until one of four scenarios occur - the player defeats all enemies, the enemies deplete all health points of the Cass or Ion, both sides run out of turns, or if the player chooses to use the Song Magic attack. The more the Song Magic is charged, the more powerful it is, and the more it works towards eliminating random battles from the area. If the Song Magic meter is maxed out, the battle is automatically won, and random battles are eliminated from the area for the duration of the time spent there.

The rest of the game's gameplay modes more closely resemble a visual novel, largely revolving around reading text and choosing from dialogue trees or other text-based options. The "Genometrics" segments are story segments where the player dives into a character's subconscious dream world to help them through various mental hang-ups they're suffering through in the game. The segments are split into 10-20 points on a map to be selected; each one revealing more of the narrative. Selecting each one costs Dive Points (DP), which are earned through participating in the game's battle system. Certain dialogue options cost DP as well, and may hinder or help progression. If the player cannot pay the given cost of DP required, progress is halted, and the player returns to the main game. The segment is completed once enough DP is spent to read all text to the story's conclusion, and completion rewards the player with new "Song Magic" to be used in the game's battle system. The game's "Purification" segments involve two characters meditating and reflecting together on various events that had transpired in the main game. The player is also given the option to equip "Genometrica Crystals" that are obtained through progression of the Genometrics segments, which give stat boosts for the game's battle system. The game also contains an item synthesis system similar to the Atelier video game series. Upon traveling to item shops, and talking to their respective shop keeper synthesis recipes are obtained. If the player has obtained the required items through game progression, they may combine them into new items. Each item creation contains a story scene about the respective item, and can be used in further synthesizing, or for added effects in battle.

The bulk of the game takes place on a massive space station traveling through space. Humanity has been traveling through space on it for the last 5,000 years following the destruction of their home planet, Ra Ciela, which was destroyed by its own sun. Morale is generally low for its inhabitants – they long to live on in nature again, the ship is running out of resources, and they've been unable to find a new planet to sustain them. Additionally, they're under attack by a fairy-like race of humanoids called Sharls, who, with their innocent appearances and power of "Song Magic", lure people away to abduct them. Humanity is generally powerless against them, and must resort to sectioning off parts of the space station and hiding, and their numbers diminish. However, after thousands of years have passed, the impassable "Fellion Wall" falls, and in are people called "ancients" - people essentially cryogenically frozen from the era when humanity still lived on Ra Ciela. It appears human from this era once also possessed the ability to create "Song Magic", and thus, these people allow for the ability to fight back against the Sharl. Alternatively, there's another cult-like faction of people who believe in giving up and disappearing away with the Sharl, complicating matters.

The game follows the events of two separate pairs of main characters. Delta, an elite fighter from the organization of PLASMA, travels with his childhood friend Cass, who has the ability to wield song magic. Both are Ancients from the city of Felion. The other pair is Ion, also able to wield rare Song Magic, and Earthes, a humanoid robot of unknown origins. Earthes is similar to a silent protagonist in the game - he is a vessel of which the player is supposed to be communicating directly into the game world, with game characters directly addressing the player, breaking the fourth wall. Other prominent characters include Nay, a friend of the four who holds a leadership role called the "Divine Empress", Kanon, a rival-turned-friend of Ion's past, Zill a church bishop who advocates working with the Sharl, Sarly a scientist friend of Delta and Cass, and Shirotaka, an otaku computer hacker friend of the groups.

Ar Nosurge was first announced in September 2013, as part of developer Gust's 20th anniversary plans. The game was directed by Akira Tsuchiya, who had previously directed Gust's Ar Tonelico trilogy of video games, and Ciel Nosurge. The games, along with Ar Nosurge, are all part of Gust's extended "Exa Pico" fictional universe. The events of the Ar Tonelico trilogy connect to each other, but largely just occur in the same fictional universe rather than directly overlapping into Ar Nosurge. Ciel Nosurge, however, is considered a prequel to Ar Nosurge, and contains many common characters and settings, with the two often referred to collectively as the Surge Concerto duology. Despite this, Tsuchiya created Ar Nosurge to be an entirely self-contained story that requires no knowledge of the other game's to understand the game's story. The game was meant to mix the anime style of Gust's other main franchise, Atelier, while added a more in-depth science fiction story element to it. The game's key concept was to create a game world that felt like an "actual existing world", where the player is playing a role in the story as themselves, using the video game console to communicate as themselves to the characters in the game. Exploring realistic and in-depth bonds between characters was a main focus for the development team as well. Some story events, such as the "Purification Ceremony" scenes, feature sexual overtones and innuendo; Tsuchiya implemented this to create more realistic interactions and relationships between characters. The game's battle system was developed to be flashy in presentation to hold the player's attention, but simple and quick in execution, as to keep the focus on the story and characters. All aspects of the gameplay were built to feed into the game's story, in order to create a better sense of immersion. Not all ideas related to creating a sense of immersion were included in the final game; at one point, the game contained enemy characters in battles that could "notice" the presence of the player, and would try to do things to "harm" the player, such as deleting their save game information. However, this was deemed too detrimental to the enjoyment of the game, and was removed prior any of the game's releases.