How can I apply for your insurance during my trip? and some stuff

Hello there, I am Japanese in Japan and planning to travel over 3months. Then, for the first 3 months, I will be using the insurance of my credit cards that last for the first 3 months. Therefore, I would like to use your insurance 3 months after I leave Japan. On top of that, someone told me that I couldn't get your insurance if I have a blank day when I don't have any insurance or something. So, when I apply for your insurance, do I have to prove that I have had the credit cards' insurance? And do you know how I can do that?

Thank you

Asked by Koichiro via WorldNomads.com