O₂ Engine is renamed to novelsphere.js!

Bringing Visual Novels to all Devices

The novelsphere.js, based on HTML5, works on Windows, Mac, iPhone, iPad and Android devices.

Compatible with KAG3

The novelsphere.js boasts compatibility with Japan's most famous novel game engine KiriKiri, and can interpret KAG scripts.


As the novelsphere.js works purely off HTML5, it is possible to run novels on modern browsers, even on mobile devices without the need for any third party applets such as Flash. This allows the engine to function on any modern browser, without the need for further extensions.


Novels created on the novelsphere.js not only function in a browser, but can be packaged as an application for iOS, Android, Windows and Mac.

Interactive Sample

This is a sample novel created on the novelsphere.js.
Through the use of the iframe tag,
it is possible to paste the game on any web page.


Free plan

Currently the novelsphere.js is specially licensed by NovelSphere. As long as the novel is published on the NovelSphere website, it is possible to download the SDK, and release/sell produced games for free.

Paid plan

In order to use the novelsphere.js on a personal platform (such as your own web page), or to release a game packaged as an application without releasing it on the NovelSphere website, a paid license is required.

Function Free Plan Paid plan
Access to the SDK and related documents
Type of release permitted NovelSphere only*1 No limitations on release
Implementation of the engine into other programs
Packaging as an application for Windows/Mac partially possible*2
Packaging as an application for iOS/Android partially possible*2
Technical support Access to the support forum

*1 It is possible to place a novel which has been uploaded to the NovelSphere website, on your own website. It will appear like the 'Interactive Sample' section does on this page.

*2 It is possible to package novels which have been released on NovelSphere, as Windows, Mac, iOS and Android applications if they are exclusively released within NovelSphere. However in the case of packaging a novel as an application outside of NovelSphere, a paid license is required.


The following are platforms or novel games which use the novelsphere.js in their production or release.


NovelSphere is a platform using the novelsphere.js, and it is designed to allow the production and release of Novel games.

 Visit NovelSphere

The House in Fata Morgana

A novel made by Novectacle, an indie game maker. It was originally a novel operating off the KiriKiri engine, however the novelsphere.js was used to conduct a port to iOS.

 Get iOS App


Ghostpia is a novel game made by Chosuido. Currently the work is available on both the web and as an application on iOS.

 Play Web App  Get iOS App


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