Japan is one of the easiest countries to travel alone, and you don't need to pack much: convenience stores and drugstores sell almost everything. But a few things make a solo trip noticeably smoother, and a few are surprisingly hard to find once you're there. Here's what to bring, what to skip, and the apps worth setting up before you fly.
Buy Me a Matcha is a free, friends-only iPhone app for meeting one new person over a matcha or coffee, all in English. No dating, and you can choose to meet only women.

Japan is generally considered very safe for women traveling alone. Normal care still applies: watch your drinks at night, keep valuables close in crowds, and use women-only train cars at rush hour if you prefer.
Cards work in most places now, but carry some yen for small restaurants, shrines, temples and local shops that only take cash.
Type A plugs with two flat pins, at 100V. Most phone and laptop chargers work with a simple adapter.
Hostel common rooms, walking tours, language exchange nights, and friends-only apps like Buy Me a Matcha, where you can meet someone in Tokyo over a matcha or coffee in English.