O₂ Engine

HTML5-based Visual Novel Engine

Latest news

Visual Novel for All Devices.

O₂ Engine is HTML5-based visual novel engine.
It works on Windows, Mac, iPhone, iPad and Android.

Compatible with KAG3

O₂ Engine interprets KAG script. It is compatible with Kirikiri, one of the most popular engine to develop visual novels.

Pure HTML5

Fully written in HTML5, therefore runs on modern browsers, including mobile. No Flash, no applet.

App Packaging

Developing novels with O₂ Engine, you can distribute them not only as web apps, but also as apps for iOS, Android, Windows & Mac.


Sample novel developed with O₂ Engine.
It is embedded in iframe,
and you can put it on your page as well!


Free Plan

Currently O₂ Engine is specially licensed for novelsphere.jp , where you're able to get the SDK and distribute/sell your works for free!

Business Plan

If you want to use O₂ Engine on your own platform, or to package your novel as an app, you can buy the business license.

Feature Free Plan Business Plan
Get SDK and Document
Publish to ... NovelSphere only Other platforms or websites
Incorporate O₂ Engine into Your Program
Package Novel as Windows/Mac Application
Package Novel as iOS/Android Application
Receive Technical Support

* NovelSphere allows you to package your novel as Windows/Mac/iOS/Android application if the novel is submitted to NovelSphere. You need to buy business license only when you want to package your novels not related to NovelSphere.


These platforms and works use O₂ Engine to distribute their visual novels.


NovelSphere is one of the O₂ Engine's licensees, where you can develop and publish your original visual novel.

Visit NovelSphere

The House in Fata Morgana

This is a work by Novectacle , a indie game maker. It is originally written as Kirikiri application, and O₂ Engine was used for transplantation for iOS app.

Get iOS App


ghostpia is a novel created by Chosuido . This novel is now distributed as an iOS app and as NovelSphere's app both.

Play Web App Get iOS App

Contact us

Feel free to contact us.
The following mailform and email address are available.

mailto:[email protected]