Tokyo is huge, but some of the best days of a Japan trip happen just outside it. These six escapes are easy to do alone: simple trains, places where walking and eating solo is normal, and enough to fill a day without a tour. Pick one for a clear day and save the city for when it rains.
About an hour from central Tokyo. Kamakura has the Great Buddha, bamboo-garden temples and hiking trails between shrines. Take the little Enoden train along the coast to Enoshima, an island with caves, a lighthouse and sunset views over the sea. It's the classic first day trip, and it works beautifully alone.
Solo tip: go on a weekday. Weekends get crowded, especially on the Enoden.
About an hour and a half from Shinjuku on the Odakyu line. Hakone is a loop of mountain railway, cable car, ropeway and a boat across Lake Ashi, with Mt. Fuji in view on clear days. Finish at a day-use onsen. The Hakone Freepass covers most of the loop.
Solo tip: start early. The loop takes most of the day, and Fuji is usually clearest in the morning.
About two hours from Asakusa on the Tobu line. Nikko's Toshogu shrine is one of the most ornate in Japan, set in a cedar forest. In autumn, the leaves around Lake Chuzenji and Kegon Falls are famous.
Solo tip: it's a long day. If you only have energy for one big trip, make it this or Hakone, not both.
About 30 to 60 minutes from Ikebukuro or Shinjuku. Old clay-walled merchant houses, a wooden bell tower and a sweet-potato snack on every corner. It's small enough to walk in an afternoon and very relaxed to explore alone.
Solo tip: try the sweet-potato soft serve. It's the local thing.
About 30 minutes from Tokyo. Eat your way through Chinatown, walk the Minato Mirai waterfront and finish with the harbor lights at night. Easy to do on a whim, no planning needed.
Solo tip: Chinatown street food is perfect for one: lots of small bites, no restaurant table needed.
About an hour from Shinjuku on the Keio line. Several trails up a forested mountain, a temple near the top and, on clear days, a view of Fuji. There's a cable car if you don't want to hike all the way. Popular, safe and very friendly to solo hikers.
Solo tip: avoid autumn weekends if you can. The leaves bring big crowds.
Buy Me a Matcha is a free, friends-only iPhone app for meeting one new person over a matcha or coffee, all in English. Meet someone who lives in Tokyo, and the next plan might be Kamakura together. No dating, and you can choose to meet only women.

Yokohama and Kawagoe are the easiest: both are well under an hour from central Tokyo by train, and you can just turn up without booking anything.
Yes. Trains are simple and reliable, the main day-trip towns are used to visitors, and eating or walking around alone is completely normal.
Usually not. Many of the best day trips use private railways like Odakyu (Hakone), Tobu (Nikko, Kawagoe) or Keio (Mt. Takao), which have their own good-value tickets.
Ask at your hostel, join a small group tour, or meet someone who lives in Tokyo first. Buy Me a Matcha is a friends-only app for meeting one person over a matcha or coffee in English, and a coffee often turns into a day trip plan.