An MVNO (Mobile Virtual Network Operator) is a carrier that provides mobile services by leasing network infrastructure (base stations, etc.) from major carriers (MNOs: Mobile Network Operators) rather than owning its own. Known in Japan as "budget SIM" or "budget smartphone," representative MVNOs include IIJmio, mineo, OCN Mobile ONE, and Japan Communications. According to Ministry of Internal Affairs statistics, MVNO subscriptions have reached approximately 30 million lines.
The biggest differences between MVNOs and major carriers are price and speed. Since MVNOs don't bear base station construction and maintenance costs, many offer plans under 1,000 yen per month, enabling significant savings compared to major carriers' 5,000-8,000 yen monthly fees. However, because they share bandwidth allocated by MNOs among many users, speeds tend to drop during congested periods such as lunch (12:00-13:00) and evening (17:00-19:00). They may not be suitable for users who frequently stream video or play online games.
Choosing an MVNO depends on your usage pattern. Light users consuming under 3GB monthly can get by with plans under 1,000 yen. Users who make many calls should check for unlimited calling options (approximately 500-1,500 yen/month). If speed is a priority, MNO sub-brands (UQ mobile, Y!mobile) and MNO online-only plans (ahamo, povo, LINEMO) are also options. These are sub-brands rather than true MVNOs, but their pricing is close to MVNOs while offering MNO-equivalent speeds.
Phone numbers can be transferred via MNP, so there's no worry about changing numbers. eSIM-compatible MVNOs are increasing, enabling same-day online switching. Using dual SIM to combine a major carrier for calls with an MVNO for data is also a popular cost optimization strategy. Review switching procedures in the number portability guide.