Sometimes you have a DVD with a small section of video you want to use in class, or want to put on your iPod, or you want to edit a little for your class use. This is legally OK because it is called Fair Use, an exception to copyright, specifically for education. HandBrake is a software you download and install on your computer to change from one format to another.There are many different video formats, and not all people can play all the formats on their computers, so a coversion software is necessary. This one is free, and works very well. This does require some knowledge of editing videos to use well. Sorry, no Japanese version available.
I use aimersoft dvd ripper, also a good dvd video converter but cost a little money.