ONScripter (O-N-Scripter) is a program that interprets a script written for NScripter in its own way.

You need to prepare game data separately.
Then, you need to create folders for each game under /sdcard/ons and place game data (nscript.dat, etc.) under those folders.
You also need to place a truetype font file named as default.ttf in the same location as game data.
If you want to play video, install an appropriate video player such as MX Player.

Please see the following web page for more details.
http://onscripter.osdn.jp/onscripter.html
http://onscripter.osdn.jp/android/