The simple reason is carrier policy. Manufacturers like Sony, Samsung, and Sharp provide official bootloader unlocking tools for their international, SIM-free models. However, when these manufacturers produce a model specifically for NTT Docomo, they are contractually obligated to disable bootloader unlocking.
For most Japanese carrier devices from Docomo or SoftBank, the official bootloader status is set to docomo unlock bootloader top
If you want the top reliability without risking a $500 brick, Japanese repair shops like or Janpara (and some online services) offer paid bootloader unlocking. The simple reason is carrier policy
Unlocking the bootloader on NTT Docomo branded devices (particularly Sony Xperia models) is notoriously difficult because these carrier variants are typically hard-locked by the provider to prevent third-party firmware installations. 1. Executive Summary: The "Hard-Lock" Problem For most Japanese carrier devices from Docomo or
By following this guide and taking the necessary precautions, users can unlock the bootloader on their Docomo devices and enjoy a world of customization and development possibilities.
Confirm the action on your phone's screen using the volume keys to navigate and the power button to select. The device will wipe all data and reboot with an unlocked bootloader. Risks, Safety Warnings, and Pitfalls