Kirikiri in Wikipedia
KiriKiri (吉里吉里?) is a scripting engine by Japanese developer "W.Dee". It is almost exclusively used with the KAG (KiriKiri Adventure Game System) framework to produce visual novels. Usually, the package of the two components is regarded as the whole engine, and referenced with major version numbers. Thus, the current version is called KiriKiri2/KAG3. It is available under the GNU General Public License, though commercial licenses can be acquired if somebody wishes to expand the software without disclosing the changes.
KiriKiri has been used in both dōjin and commercial visual novels, the most well known of which are TYPE-MOON's Fate/stay night and Fate/hollow ataraxia. It is often used as a more modern and expandable replacement of the older NScripter engine.