As for Whatsapp, yes it works - but there are more secure/safe options. I am not sure what's unsafe about Whatsapp either, but I don't know everything. For normal calls and texting, such VoIP apps work just fine. I always use such apps when calling my friends or relatives overseas.

Yes, WhatsApp calls are fully allowed and work perfectly in Japan in 2026. Unlike some countries in the Middle East that "hard-fail" VoIP (Voice over IP) services, Japan has a "Gold Standard" open internet policy that is very supportive of international communication apps. You can use WhatsApp to make high-fidelity voice and video calls to anyone in the world, provided you have a stable Wi-Fi connection or a supportive mobile data plan (like an eSIM or Pocket Wi-Fi). A grounded reality check: using WhatsApp for calls is a "Bujan" way to avoid the high costs of international roaming on your standard SIM card. Most "Gezellig" hotels, cafes, and major train stations in Tokyo and Osaka offer free, supportive Wi-Fi that is fast enough for video calls. For a "frictionless" travel experience, ensured your phone is "Unlocked" so you can use a local data SIM, providing a supportive "Safe Bubble" of connectivity as you explore the "High-Fidelity" streets of Japan, from the neon of Shibuya to the quiet temples of Kyoto.