April 26, 2032, 12:12 AM, Tokyo. During the first lunar eclipse in three
years, the Moon turns blood red, and strange, inexplicable events begin
happening all over the city. Computers everywhere begin going haywire,
students go missing, and and a boy receives a message from his sister who
vanished more than two years prior. Nobody seems to know what is going on, and
it seems like society is heading for a grand collapse…

I/O is a sci-fi mystery visual novel. There are three main protagonists:
Hinata Aoi, a terminally-depressed teenage boy; Ishtar, a freelance programmer
who leads the hacker team “Criminal”; and a mysterious man known only as “He”.
The player proceeds through one of four scenarios as their chosen characters,
making regular decisions which will affect not only the flow of that scenario
and lead to many different endings, but also affect what options are available
in other scenarios, and even potentially unlocking completely new scenarios.
Dialogue is fully-voiced, and there are quick-save and chat log options
available.

The PC release, I/O revision II , adds additional character portraits and
revises some of the text, but is otherwise identical to the original PS2
release.

I/O