Japan had a strong flip phone ecosystem back when iPhone happened. Contactless payment, lootbox microtransactions, music downloads, GIF emojis, TV broadcast, multicore CPUs, Linux-based OS, biometrics, >326ppi displays before iPhone 4, 3x mechanical zoom, literally everything. Sadly the industry was focusing razor sharp on political infighting and was just building up crufts, and so the UI/UX was beyond atrocious - it was not simply outdated, the entire ecosystem was user hostile. That and downright illegal quota enforcement from Apple wiped it out.
Two major mistakes made by Japanese phone manufacturers was that they didn't ship the phones globally from being scared to death with language barriers, and that no one cared about horrible organizational mess.
They had a decade and half to make MOAP(L) work out as a usable touchscreen OS that runs on Renesas SH processor with Toshiba DRAM and paired with a Fujitsu modem, they didn't take that route and instead spent that engineering man-hours on processing PDF file returned from payment gateway on a phone, and let it all bleed out.
IIUC, Korea was in an almost exact same situation. They managed to come out of it. Japan could not.