The Xperia Z4 SOV31 is a smartphone developed by Sony Mobile. It was released for the Japanese domestic market by KDDI and Okinawa Cellular Telephone Company under the au brand, featuring support for 3.9G (au 4G LTE / au VoLTE) and 4G (au 4G LTE CA / WiMAX 2+) mobile communication systems.
Overview On June 11, 2015, the Japanese telecommunications carrier KDDI launched the Sony Xperia Z4 (model number SOV31) as part of its summer product lineup. While the device was released across all three major Japanese carriers—with NTT Docomo launching its version on June 10 and SoftBank on June 12—the core hardware specifications remained uniform across all variants.
At launch, the outright purchase price of the SOV31 on the au Online Shop was 84,240 JPY. KDDI offered a monthly discount program ("Maitsuki Wari") totaling up to 41,040 JPY (distributed as 1,710 JPY per month over 24 months). For Mobile Number Portability (MNP) customers, an additional discount of 16,200 JPY was applied under a two-year contract. Consequently, the net effective price was 43,200 JPY for new contracts and upgrades, and 27,000 JPY for MNP transfers.
Furthermore, the device was eligible for the "au Kaeru Wari Plus" campaign; under this promotion, MNP customers subscribing to eligible contracts could receive either two years of waived basic monthly fees (under legacy plans) or a cashback bonus of 10,000 JPY (under newer plans).
It was upgradable to Android 7.0 Nougat on March 30, 2017.
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