I would say yes and no. There's no designated cycling lane so it can be a little dangerous but driver's are a lot safer in Japan. But then again I have also heard about people being hit by cars and I've also heard about a lot of people accidentally running into pedestrians on the sidewalk so it COULD be dangerous for both the cyclist and the pedestrians. But just make sure that you are careful and make sure you have insurance and you should be fine.

I'm actually planning on traveling to Japan again in the next few months and the last time i was there i didn't have a portable wifi or a sim card and now i know i definitely need one so I was wondering if anyone could recommend something to me? I've seen a few places on the narita website like global advanced communications https://www.globaladvancedcomm.com/pocketwifi.html and genki mobile https://www.genkimobile.com does anyone know these companies? are they any good?

I would say yes and no. There's no designated cycling lane so it can be a little dangerous but driver's are a lot safer in Japan.
But then again I have also heard about people being hit by cars and I've also heard about a lot of people accidentally running into pedestrians on the sidewalk so it COULD be dangerous for both the cyclist and the pedestrians. 

But just make sure that you are careful and make sure you have insurance and you should be fine.