Hikari Denwa is an IP phone service provided by NTT East/West that uses fiber-optic lines (FLET'S Hikari). Built on VoIP technology, its distinguishing feature is that it can be used just like a traditional analog phone. As fiber-optic access spread, it grew into the service that many households move to when they give up a copper analog line.
There are three major differences from 050-number IP phones. First, in most cases you can keep your existing landline number (with area code), which spares you from reprinting business cards or editing your website. NTT East does note, however, that there are cases where a number cannot be carried over (as of August 2026), so confirming that your number survives the switch is the first practical step before you apply. Second, it supports emergency calls (110/119), which 050 IP phones cannot make, a difference that matters in an emergency. Third, call quality is comparable to analog phones, as voice is transmitted within NTT's closed IP network, designed to be less affected by internet congestion.
Charges break down into a monthly base fee and call charges. With NTT East, the standard Hikari Denwa plan costs 550 yen per month including tax, and the separate "Hikari Denwa A (Ace)" plan costs 1,650 yen including tax (both as of August 2026; NTT West pricing has to be checked separately). At the same point in time, the line usage fee for an NTT subscriber telephone runs 1,980 to 2,090 yen per month including tax for a residential push-button line, varying with the exchange class, so on base fees alone Hikari Denwa is the lighter option. It does require a FLET'S Hikari subscription or a fiber line from a collaboration provider, so compare the total including internet charges. For a household already on a fiber line, the only addition is the phone-side base fee and call charges. Call charges depend on the plan and the destination, and a universal service fee and a telephone relay service fee are billed on top, so check the official rate table for the breakdown before you sign up.
Note that Hikari Denwa cannot make calls during power outages. Analog lines operated on minimal power supplied from the telephone exchange and worked during outages, but Hikari Denwa requires power for the optical network unit (ONU) and router. Installing a UPS (uninterruptible power supply) or keeping a mobile phone as backup is important. Review migration procedures in the Hikari Denwa migration guide and technical background in VoIP basics and benefits.