Field of study and research plan for the MEXT master's degree program

Hi. I really want to apply for the MEXT scholarship for a master's degree but I have some problems. I just finished my bachelor's degree in mathematics. I have no idea what a research plan is. I tried to read about this but I still need help. How should I find a research theme? will I choose it myself? How should the research plan be written to maximize my chance?
thanks...