Good mobile data contracts for 5 weeks hike

Hey guys, question here:I will be hiking 5 weeks through japan and propably need some wifi on the way to navigate and stuff. Im from germany an will arrive early august if thats a useful information. I dont want to be „scamed“ at the airport or something, so im hoping you have some tips for me. 🙂

https://www.reddit.com/r/japan/comments/154lz7q/good_mobile_data_contracts_for_5_weeks_hike/