With the PPV fight costing about $100 USD in most places, I just found about an on-demand and streaming sport site called DAZN, it is available only in Japan, Germany, Austria and Switzerland.
They will live streaming the fight, and have the rights to a whole other sports and various leagues.
The most important thing is that they offer a 1 month free trial and after the trial the subscription costs 1800 yen per month (tax inc).
Check them out if interested, i just started my 1 month free trial about 30 min ago. My initial impression is that they seem to have a good amount of content and the video quality is very good, also the site can be set to English
You will need a credit card to start the trial and subscribe, dont know if international credit cards will work. I used my japanese CC