This chart, from JEITA, shows phone shipments from domestic Japanese manufacturers. The series are cellular and PHS, the Japan-only limited mobility system.
Part of this collapse is driven by migration away from domestic OEMs that were strong in featurephones to foreign smartphone makers, mainly Samsung and Apple. However, it seems to start too early for that to be the only explanation: there certainly weren't 20m iPhones and Androids sold in Japan in 2009. Other market dynamics at play (10 years ago I knew a lot about this market, but I haven't been paying close attention recently). Either way, the pain inflicted is pretty obvious.