Whether you live in Tokyo or are importing a phone to the West, here is the reality check.
One of the earliest fruit of this labor was the , a rebranded Samsung Omnia, followed quickly by the Galaxy S (SC-02B) . The SC-02B was a watershed moment. It introduced Japanese consumers to the brilliance of Samsung’s Super AMOLED displays. While Japanese manufacturers were still clinging to smaller screens and physical keypads, the Galaxy S offered a large, vibrant canvas that made mobile internet browsing a genuinely enjoyable experience.
Japanese carrier models have notoriously locked bootloaders. You cannot install custom ROMs like LineageOS on a Docomo Galaxy S series.