A sci-fi suspense adventure game developed by Regista, it begins with a total lunar eclipse in Tokyo in 2032 and a computer anomaly. High school student Aoi Hinata, searching for his missing sister, programmer Ishtar, and other protagonists investigate from their respective circumstances, gradually piecing together the full story of the case from different paths.
| Title of the work | I/O |
|---|---|
| The publication date listed in the materials | 2006-01-26 |
| Platform | PS2 / PC |
| Genre | A sci-fi suspense adventure AVG |
| Also known as | I/O revision II |
| Development | レジスタ |
| Release | GN Software（PS2）、アスガルド（PC） |
| Script | Takumi Nakazawa (Scenario Draft, Design & General Supervision, E Route & E' Route Writing), Nobuaki Kenbe (Scenario Plot, Design Cooperation, Overall Supervision & A Route Writing), Aoi Takagi (B Route & B' Route Writing), Hiroyuki Ohara (C Route & C' Route Writing), Hirohiro Hata (D Route, D' Route & A' Route Writing) |
| Key animation | SOYOSOYO [Hiroshi Shiono] |
| Music | onoken |
| Director | Takumi Nakazawa (PS2), Daisuke Sato (PC) |
| Producer | Takumi Nakazawa, Kuniharu Hosoda |
| Game engine | Yeti/Regista Engine |
| Website address recorded by the source | http://www.regista.co.jp/io/ |
| External links to source records | https://erogamescape.org/~ap2/ero/toukei_kaiseki/game.php?game=6331 / https://vndb.org/v96 |
Source: Structured works maintained by the Bangumi community, filtered and rearranged by this site.
Two story entrances after a lunar eclipse
The original official website sets the story in Tokyo in the early hours of April 26, 2032: a total lunar eclipse and an unexplained computer anomaly occur simultaneously, followed by unexplained events, terrorist activities, and cybercrime. Route A unfolds from the situation of high school student Hinata Aoi; He receives a distress email claiming to be from his twin sister Yumezuki, who has been missing for two years, and, with the help of his childhood friend Sakuya Kawahara, searches for her whereabouts.
The B line follows the freelance programmer Ishtar. She leads the hacker team Criminal in system construction and security checks. The team clashes with mysterious intruders and gradually becomes involved in the confrontation with the cyber terrorist group Code.
People and urban spaces
The original character page confirmed that Hinata and Yumezuki were twins. After Yumezuki disappeared, Hinata's sense of alienation and helplessness deepened; Sakuya is a friend he has known since childhood and still keeps in touch with. Ishtar is both a freelance programmer and the head of Criminal. The two entry points focus on different people and issues; readers need to gradually understand the same world through the experiences of their respective protagonists.
The stage page places the Hyuga Line mainly near residences, schools, and parks on the west side of the city, while the Ishtaru Line is mainly placed on the east side around shopping streets, warehouses, and data centers. In this near-future society, home appliances and communication devices were widely connected, but the street scenes still retained an appearance similar to that of Japan at the time.
4. Main Characters and Branching Reading
The original system page explains that at the start, players can choose one of four protagonists and advance the text adventure through dialogue or actions; Choices can change the direction and outcome of the story. Each route first presents different segments, and after completing the stories of multiple protagonists, the scattered information gradually comes together.
Specifications of the work
Regista labeled "I/O" as SF Mystery Adventure. The PS2 version was released on January 26, 2006, in Japanese, and published by GN Software. Product information lists both the regular and limited editions, labeled CERO C, for ages 15 and above.
Division of Creative Responsibilities
Regista's official credits list planning, original concept, director, programming, scriptwriting, and production roles; The original concept was co-written with Romeo Tanaka, with the script jointly written by Regista and Nobuaki Kenbe. The publishing brand GN Software and the producer Regista are responsible for product distribution and development, respectively.
Windows version
The Windows product released in 2008 was titled "I/O revision II," published by Asgard and developed by Will. Regista credited it as a production collaborator and stated that the original work was Regista's "IO." The Windows version is labeled CERO A; The original PS2 version was CERO C.
School, twins, and hacker teams
Aoi Hinata acts to track down his missing twin sister Yumetsuki, and his childhood friend Sakuya takes care of him. Criminal is led by Ishtar, with members including Mika, skilled in hardware; Kosuke, who lightens the mood; and the newly joined twins, Masami and Mayumi, each using different codenames.
Two editions were produced and attributed to the two editions
The PS2 version was co-designed, developed, and produced by REGISTA, with a co-concept with Romeo Tanaka and a co-script by Nobuaki Kenbe; In 2008, Windows revision II was released under the ASGARD brand, with Will Development and REGISTA production cooperation.
PS2 version: Entry links and additional clips
The PS2 version links keywords with hyperlinks, allowing players to search related content along the terms. After completing Route A, new fragment scenes will also unlock.
PS2 Route A: Character solving and player control
Route A features Hinata solving crossword questions, with the character completing the answers through the narrative while the player watches.
PS2 version: Team Action, Rewind, and Epilogue
Route B mainly depicts the joint actions of the five Criminal members. Route C gradually traces back from the future, presenting experiences in a different order.
Nagomi Yuu's PS2 completion log distinguishes between the end of Route B and the epilogue that does not appear when responding coldly to companions.
Original official website development period text: Ping to confirm the existence of the other party
The original 2005 archived official website explained the "ping" in hacker conversations: sending a presence confirmation signal to the other end of the network, and the valid system returns "pong." Characters use this affirmative language in everyday conversation; There are also claims like "no response" or "slow response," as well as "system dead" or "very serious."
Source: Structured works maintained by the Bangumi community, filtered and rearranged by this site.
Related entries
- Characters:Hinata Aoi (I/O)
- Characters:Aoi Yumezuki (I/O)
- Characters:Sakuya Kawahara (I/O)
- Characters:イシュタル（I/O）
- Characters:Mika Ayase (I/O)
- Characters:Kosuke Miyata (I/O)
- Characters:Masami Shinozuka (I/O)
- Characters:Mayumi Shinozuka (I/O)
- Setting and Setting:Criminal（I/O）
- Release Version:I/O revision II (Windows version)
- Joint Original Proposal:Romeo Tanaka
- Co-script:Nobuaki Kenbe
References
- Bangumi works entry: I/O
- Bangumi Copyright Notice
- Regista: I/O PS2 product information
- Regista: I/O revision II product information
- Regista Original Official Website Archive: Story
- Regista Original Official Website Archive: Character
- Regista original official website archive: Stage
- Regista Original Official Website Archive: System
- Yusuke Nagomi: I/O PS2 version gameplay diary
Source author: Bangumi article contributor and community maintainer; License: CC BY-SA 3.0 (https://creativecommons.org/licenses/by-sa/3.0/); Adaptation: This site filters and reorganizes structured facts, without copying the article summary.
Data compiled on: 2026-10-10.