For travelers in Japan, the cheapest is 1 GB for 7 days at $10.56. For more extended stays, 2 GB for 15 days costs $17.26. For higher data needs, 3 GB for 30 days is $22.76, 5 GB is $37.26, 10 GB is $60.83, and 20 GB is $102.50. The 1 GB plan is the most cost-effective at $10.56.