I/O

Also known as Input Output. This is the first original game by the company Regista, founded by Takumi Nakazawa of the Infinity series (Never 7, Ever 17, and Remember 11) fame, and a collaboration between Nakazawa and Romeo Tanaka (of CROSS†CHANNEL, Kana: Little Sister and Yume Miru Kusuri fame).

I/O takes place in the year 2032. A lunar eclipse occurs in late April, causing a surge of terrorist activities and bizarre incidents. As time goes on, things get worse and worse, with the key to the mystery seemed to be locked away in the MMORPG "Babylon". Four people, through their own ways, investigate the ongoing phenomenon, each one dealing with his or her own problems...

I/O, like the Infinity series, has multiple protagonists, in this case four. Route A features Hinata Aoi, an Ordinary High School Student who has become depressed after the disappearance of his twin sister, Mutsuki. Route B features Ishtar, a young woman in charge of a hacking group known as Criminal. Route C also features Ishtar, but she seems different from herself in Route B. Route D features "He", a mysterious man who is a legend on the Internet. Once all four of their routes have been completed, they unlock Route E, the true route.

The game was originally released on the PlayStation 2 in 2006, but was given an Updated Rerelease on the PC two years later, with new CGs and slightly updated artwork.

Not to be confused with the web comic 1/0.

Tropes used in I/O include:

Ambiguous Gender- Enlil, who is never specifically identified as a man or a woman. Route E finally confirms that Enlil is a woman.
Angsty Surviving Twin Mayumi, though notable in that she seems to treat her sister's death on equal level with the rest of her comrades' deaths.
Arc Words- "The beginning is the end, and the end is the beginning."
Artificial Human- "He", whose body is 2/3rds mechanical.
Ascend to a Higher Plane of Existence- Some of the villains plans. This happens to Criminal at the ends of Routes E and B'.
Assimilation Plot- Goals of other various villains.
Badass- "He" lives and breathes this trope.
Badass Longcoat- Once again, "He".
Bad Future- Routes C and D.
Bifauxnen- Enlil. Mutsuki describes her at one point as having "the body of a woman, but the mind of a man."
Big Bad- While there is no one Big Bad in the whole story, virtually all the origins of them can be traced back to eXarch.
Bittersweet Ending- Route E. Mutsuki has finally been saved and everything has finally calmed down, but the rest of Criminal is still dead, Enlil is on the run, Sakuya is nowhere to be found, and Mayumi hasn't shown herself to Hinata in a year.
Bolivian Army Cliffhanger: If you haven't cleared the routes required to see their full endings, Route B and C end this way.
Brilliant but Lazy- Hinata is very intelligent and is shown to be able to solve complicated problems in seconds, but he's so apathetic towards life that he's just not interested in it (much to Sakuya's consternation).
Brother-Sister Incest- While nothing explicit happens, there's a lot of subtext between Hinata and Mutsuki, who is practically obssessed with his sister. Lampshaded several times, particularly where he questions Yayoi whether or not he has a sister complex.
Butt Monkey- Kosuke, who seems to exist to get verbally abused by the other members of Criminal.
Chekhov's Gun- Some seemingly throwaway bits of conversation between Hinata and Yayoi early in Route A turn out to be vital in figuring out the mystery later on.
Chekhov's Gunman- Mayumi, who goes from being a supporting character in Routes A and B to one of the two main protagonists by the end of game.
Cloning Blues- Sakuya, who is actually a clone of her former self (also named Sakuya), who was killed in a car accident.
Contemplate Our Navels- The characters go into this occasionally, especially towards the end of Route E.
Cool Shades- "He" has a pair.
The Cracker- The cyberterrorist group "Code" is composed of these.
Cyberspace
The Danza- Kosuke Miyata, who is played by Kosuke Toriumi.
Disappears Into Light- Lem, after her death.
Driven to Suicide- Isaiah Nagy, who fried his biocomputer after uploading his consciousness online to escape from eXarch's research facilities.
Drowning My Sorrows- Mr. Miyata, Kosuke's father, does this for several months after the death of his son. Notable in that its mentioned he originally quit drinking and smoking after Kosuke was born.
Downer Ending- Route B, which ends with everyone in Criminal dead or severely injured, while Sakuya's fate is left completely up in the air.
Easily Forgiven- Enlil, though it's played with that Hinata and Mayumi have to be told by others to let go of their grudges against Enlil first.
Electronic Eyes- Mayumi, who gets a cyber eye to replace her lost one, which allows her to use Imaginary Vision.
Emergency Transformation- Hinata is forced to have 2/3rds of his body replaced with mechanical parts in order to save his life after being severely wounded by Enlil.
Eye Scream Mayumi gets her left eye shot out at the end of Route B.
Eyes Always Shut- Ningirsu.
Forgotten Fallen Friend- While not exactly fallen, Hinata pretty much never gives Sakuya any thought after he leaves her after Route A, but is eventually subverted in Route A', where his main focus becomes finding her. Averted hard with Mayumi, as she frequently thinks about death of her comrades.
Future Badass- Ishtar in Route C and "He", who are Mayumi and Hinata, respectively.
Gainax Ending- Route E'.
Gender Blender Name- Enlil's real name, Tsukasa, is a name usually given to boys. When Hinata hears her name, he assumes she's a man.
Genki Girl- Lem, the fairy from Babylon.
Girl in a Box- This is what happened to Mutsuki.
Goggles Do Nothing- Route C Ishtar wears a pair of goggles/sunglasses on her head that she never wears.
Guide Dang It- This game is incredibly difficult to clear if you have no idea what you're doing.
- Specifically, there are initially four routes. Sounds simple enough. What the game doesn't tell you is that you have to get a certain other ending to see the full ending of another route. If you don't, then you are left at a "cutoff point", which seems like the ending, but isn't. (In order to see Route A's full ending, you have to clear Route C, Route D must be cleared to see Route B's full ending, Route B needs to be cleared for Route C's ending, and Route A needs to be cleared for Route D's ending). Then you unlock Route E, which, if you clear that, opens up four new routes which must be cleared, and it is then and only then that you can see the True Ending. Sound complicated?
Gun Porn- One scene in particular in Route D is practically devoted to discussing the specs of "He"'s weapons in great detail.
Half-Identical Twins: Hinata and Mutsuki have very similar body structures despite being fraternal twins. As it turns out, they're actually identical twins who grew in the same placenta as a way to test the possible growth of Imaginary Children.
Heel Face Turn- Enlil.
Heroic Sacrifice- Subverted in Route B': Ningirsu attempts to do this by letting his teammates go ahead while he's stuck next to dynamite, but it's subverted when the sprinklers in the building activate, defusing the dynamite.
Hey, It's That Voice!
- Perhaps due to Romeo Tanaka's influence, this game shares several voice actors with Yume Miru Kusuri, such as Michihiko Hagi (who voices Hinata in I/O and Takeshi in YMK), Ryoko Tanaka (who voices Sakuya in I/O and Mizuki in YMK), and Kayo Nagata (who voices Mutsuki in I/O and Nekoko in YMK). Incidentally, the two games were released a month apart from each other.
Hope Spot- At the end of Route B, it looks like Criminal and the others are finally going to make it to the helicopter pad... and then Hinata's father gets shot. It all goes downhill from there.
I Want My Beloved to Be Happy- Mayumi acknowledges that while she loves Hinata, he has Sakuya, and so she resolves to let them be happy together. However, in the ending of Route B', where Hinata is unable to save Sakuya, it's implied that Mayumi will eventually confess to Hinata.
Inferiority Superiority Complex- Masami, who's haughty attitude is used to hide the fact that she feels inferior to her sister Mayumi, who is more loved by the rest of the members of Criminal. Ironically, Route C' reveals that Mayumi also felt inferior to Masami.
It's Not You, It's My Enemies- Hinata uses a variation of this to leave Sakuya.
It's Personal- It's eventually revealed that many members of "Code" are actually normal people who had relatives who worked at eXarch that got killed off by them, hence why their main target is eXarch.
Japanese Ranguage- Actually used as a plot point once. When trying to solve Mutsuki's crossword puzzle, Hinata can't figure out the clue for the word "Lunar Excursion Module" due to the lack of an L in Japanese, and so is stumped until Mayumi helps him. She even lampshades the trope.
Journey to the Center of the Mind- Hinata and Mayumi have to do this to awaken Mutsuki by diving into her brain in the Enigma system. However, this gets them trapped into an infinite loop by "Marduk".
Kill'Em All- The ending of Route B.
- Several bad endings also count.
Legacy Character- Ishtar becomes this, with Mayumi taking up the role of "Ishtar" after Route B.
Les Yay- Mika seems to look up to Ishtar a little too much at times, with later routes making it quite clear that she views Ishtar as more than just a friend. In a serious, canonical example, Enlil and Mutsuki are in love with each other.
May-December Romance- Mutsuki fell in love with Enlil when she was only 12 years old.
Meaningful Name- Several, some of them Lampshaded in-story, while others come from Word of God:
- When reversed, the kanji in Hinata Aoi's name forms the kanji for "sunflower".
- The kanji in Mutsuki's name literally mean "dreaming moon".
- If you take out the middle kanji in both Mayumi and Masami's names, you get the kanji for "truth". This is explicitly pointed out by Ishtar at one point.
- Isaiah Nagy (the first IC and the source of "He") and Nami Izawa (Ereshkigal) both have similar roots: Reading the first part of Isaiah's first name and last name yields "Izanagi", while reading Nami's name in the Japanese order yields "Izanami", the god and goddess of creation in Japanese mythology.
Mesopotamian Mythology- A major theme in the game, with characters, locations, and terms being named after Babylonian and Assyrian mythological terms.
Mismatched Eyes- Ishtar, who is specifically noted to have heterochromie.
Oblivious to Love- Hinata seems completely unaware of Sakuya's rather obvious feelings for him. Route A' subverts this, where it reveals he was aware of her feelings, he just didn't feel like he could accept them in his mental state at the time.
One Steve Limit: Subverted, there are two "Sin"s in Babylon: the original one, Mutsuki, and the new Sin, who is a drug dealer and a member of "Code". The latter ends gets killed by Enlil in the real world for disgracing Mutsuki's name and for abusing his power.
Powered by a Forsaken Child- The Enigma system, which is powered by Mutsuki by putting her a sleep that lets her brainwaves control the system.
Playful Hacker- Many, but especially Ishtar, who one time manages to make a program to delete viruses like a shooting mini-game.
Put on a Bus- After the end of Route A and her brief appearance in Route B, Sakuya just disappears from the plot altogether. She eventually reappears in Route A'.
Rapunzel Hair- Ishtar. Ereshkigal's hair is even longer.
Refusal of the Call- In one of Route B's Bad Endings, Ishtar refuses to stop "Code"'s assault on eXarch, and instead has Criminal run away to a remote island. Unfortunately for them, The Call Knows Where You Live...
Robotic Reveal- "He" in Route C is revealed to have a mechanical left arm.
Sacrificial Lion- Mika in Route B.
Shrinking Violet- Mayumi.
Shout-Out- A subtle one to Ever 17. Hinata's reaction to looking in the glass after a month of being unconscious and discovering his appearance has changed is almost exactly the same as Hokuto's reaction to looking in the mirror and seeing his appearance for the first time.
- There are more to various pieces of literature, such as Alice in Wonderland, The Once and Future King, Macbeth, The Epic of Gilgamesh, A Connecticut Yankee in King Arthur's Court, Do Androids Dream Of Electric Sheep... the list goes on.
Sole Survivor- Mayumi is the only member of Criminal who survived the assault on eXarch.
Soundtrack Dissonance- "Subnetwork", a rather calm, soothing theme... which often plays as something bad is happening or when people are dying.
Stalker with a Crush- Andras to Mika, which traumatizes her horribly. In one of the Bad Endings, he ends up killing her, while in another, she shoots him dead.
Sunglasses at Night- "He" always wears sunglasses, regardless of time or place. When he does take them off, it's to signify that he's fully speaking as Hinata at that moment.
Super-Powered Alter Ego- This is essentially the relationship between Hinata and "He": after "He" is downloaded into Hinata, he can use his body to fight, but both Hinata and "He" are existing at the same time, and don't require to "shift" or anything. However, Hinata has none of "He"'s abilities.
Surprisingly Good English- With a few exceptions, the written English in the game is correct, both grammatically and spelling-wise.
Survivors Guilt- Mayumi. The scene where it hits her is even called "Survivor's Syndrome".
Talking to Himself- Twins Mayumi and Masami Shinozuka, who share the same voice actress. "He" shares a voice with Hinata, "Ashur", and Isaiah, while Lem shares a voice with Mutsuki "Marduk", and Ereshikigal. There are also several other characters in the game who share voice actors, but that's more due to the limited voice cast rather than other reasons.
Take Up My Sword- Ishtar to Mayumi at the end of Route B, giving her the rosary that her "Onee-sama" gave to her, as a sign that her role has ended.
Taking the Bullet- Kosuke dies in Route B after taking a bullet aimed at Mayumi and Masami.
- In Route E, Lem does this for Mayumi (with Ishtar's appearance), taking a bullet aimed for her.
Cool Big Sis/ Team Mom- Ishtar for the rest of Criminal.
Technical Pacifist- During the raid on eXarch in Route B, Kosuke notably selects a tranquilizer gun as his weapon.
Theme Naming- Many characters, locations, and terms are named after entities from Babylonian/Assyrian mythology, and there are many allusions to said mythologies.
Tomato in the Mirror- Ishtar in Route C is actually Mayumi, who took up Ishtar's role after Route B.
- Also done in Route D, where it reveals that "He" is actually Hinata, but as this is revealed in Route C and is heavily hinted in the route, it's not as much as a surprise.
Took a Level in Badass- Hinata and Mayumi, but especially Hinata, who squares multiple levels at once when he becomes "He".
Tragic Keepsake- After his father's murder, Hinata wears the chronograph that his father once wore.
Tsundere- Sakuya for Hinata and Masami for Kosuke.
Twin Switch- In an additional scene in Route B, Masami attempts to pretend to be Mayumi in order to confess to Kosuke, since she thinks Kosuke likes Mayumi more. However, Kosuke quickly sees right through her, and tells Masami that though he likes her, he doesn't like her in that way.
Victorious Childhood Friend- Sakuya in Route A'.
Virtual Ghost- Shadow Nulls, who are essentially the remainders of someone who used Cyberspace frequently, and can continue to live after death in that world, but cannot interact with the real world unless they have someone living to do it through.
Where Are They Now? Epilogue- Route E's epilogue shows Hinata, Mayumi, and Mutsuki one year after the end of the game.
Yandere- Enlil, who's very possessive of Mutsuki.