Two weeks in Japan uses less data than people expect — once you know what really drains the meter.
What actually uses data
Navigation and image translation account for most daily use. Budget 350–500 MB a day for ordinary sightseeing, video aside.
The right size
10 GB over 15 days comfortably covers two people if hotspot use stays occasional. Below 6 GB, plan on a top-up.
Networks and coverage
Syla rides on NTT Docomo and KDDI, so coverage holds up in cities and on trains, including mountain lines.
syla: download offline maps at the hotel — it is the easiest saving there is, roughly 1 GB across a trip.