>>2072380Any train that gets you the fuck out of the Tokyo concrete heat island, Isesaki hit 41.8°C (107.2°F) last August, central Tokyo wasn't much better at 40°C flat. Preferably one that gets you somewhere elevated or north, and where you can also see stuff so you're not just taking a train.
Near Tokyo:
>HakoneYou get to take the Romancecar, Hakone Tozan with it's twists and switchbacks, the funicular, and then a cable car to the actual Hakone part with a bunch of things to do.
>Nikko/KinugawaThe Spacia X is a nice train, and it gets you either near the touristy bits of Nikko, or right in the middle of Kinugawa and it's onsens.
>Koumi LineOn some days, HIGH RAIL 1375, a stargazing-themed train that looks nice on it's own, has a run from Kobuchizawa that has a dedicated break for stargazing, although the weather might ruin it. From terminus in Komoro you can still catch a train to Karuizawa to spend the night there.
Further out:
>Kurobe GorgeA small loco pulling tourist cars through beautiful valleys, tunnels and bridges.
>Ou Main Line/Gono LineTake the Resort Shirakami, which has been posted in /jrg/ several times before. My recommendation is to start in Akita and then get off at Hirosaki instead of going all the way to Aomori, and spend at least one day there(although I did spend the day after in Aomori). Keep in mind the tickets can be hard to get even normally, and around Nebuta Festival in early August they're highest grade unobtanium(along with sensibly priced accommodation anywhere closer than Morioka).
>Tadami LineBeautiful scenic line with what are technically regular local trains(so cheap and no reservations) running three times a day, and the line was rebuilt recently after floods and heavy rain destroyed it.
Also don't go to Chichibu, when I went there last summer it felt hotter than central Tokyo, and frankly there isn't that much to see, even the AoHana stuff was mostly replaced by some fujoshit the city collabed with when I got there.