What are the best day trips from Sapporo?

Otaru over everything else for a single day. Thirty-five kilometers west of Sapporo, 32 minutes on the JR Rapid Airport line — trains run roughly every 20 minutes from Sapporo Station, around ¥750 ($5) each way. The canal is the postcard shot, and it's worth seeing, but the real draw is Sakaimachi-dōri, the old warehouse street running parallel. You might spend an hour at Kitaichi Glass, where you can blow your own piece together — one of those activities that works whether you're both into craft or one of you just wants to watch and drink tea at the café next door. For lunch, skip the conveyor-belt sushi places near the station. Head to Sushi-ya Dōri instead — Otaru's dedicated sushi row — where the uni comes from Shakotan Peninsula and tastes like cold seawater and butter. Counter seats at most of these places, so you're shoulder to shoulder, which for two people who actually like each other is better than a formal table. Walk the canal around dusk before catching the train back. The gas lamps flicker on around 5pm and the water goes still. Best two hours of the whole trip.

Jozankei is the low-effort option, and I mean that as a compliment. Twenty-six kilometers south of Sapporo, the Jotetsu Bus from the station terminal takes about 75 minutes and costs around ¥800 ($5). The town sits in a river gorge where the Toyohira River cuts through forested hills — in October the maples turn and you'll understand why half of Hokkaido drives here, but in early summer the gorge is quiet and the air smells like wet cedar. Hoheikyo Onsen is worth the extra 10-minute bus ride past the main town: an outdoor rotenburo fed by milky sodium-chloride water, forest pressing in on all sides, a view straight up the gorge walls. Water temperature tends to sit around 42°C — hot enough that you ease in slowly, cool enough to stay an hour. For couples who want to bathe together, several Jozankei ryokan rent private kashikiri baths by the hour. This is the trip for when one of you wants to hike the gorge trail (about 4 km, flat, 90 minutes) and the other wants to dissolve in hot water all afternoon. Check the Jotetsu return schedule before you commit — the last bus back leaves earlier than you'd guess.

Noboribetsu is the dramatic one. A hundred kilometers south on the JR Limited Express Suzuran — about 75 minutes from Sapporo Station, roughly ¥4,500 ($28) reserved seat each way, then a 15-minute local bus from Noboribetsu Station up to the onsen town. Jigokudani hits you before you see it: the sulfur smell rolls downhill like a warm blanket of rotten eggs, and you either find this thrilling or want to leave immediately. The valley itself is a 10-minute walk from the bus stop, and the boardwalk loop takes maybe 45 minutes. Gray mud pools bubble and steam vents hiss through orange-stained rock — it looks like another planet. Dai-ichi Takimotokan has the largest public bath complex in the area, somewhere around 35 pools fed by different spring types, from iron-red to sulfur-white. The honest trade-off: Noboribetsu as a day trip is tight. You'll likely arrive around 11am and need to catch the 4:30pm return bus for the 5pm Suzuran back. That gives you five hours — enough for Hell Valley plus one long bath, but not both plus a sit-down lunch. If you have two days, stay overnight. One day, go — but know you're choosing.

Lake Shikotsu is the quiet card. Fifty-five kilometers south, Chuo Bus runs from Sapporo Station in about 80 minutes for around ¥1,100 ($7). The lake is a caldera — water so clear you can see the bottom at 20 meters — and the whole place feels emptied out compared to Otaru's crowds. Paddle boats rent for around ¥2,000 ($12) per hour if you want to be on the water together; the lakeshore walk to Poropinai takes about 40 minutes, and the only sound is gravel underfoot. That said, bus frequency is thin — three or four departures daily — so check the timetable before committing. For couples where one wants the volcanic drama of Noboribetsu and the other wants a still lake, the two are only about 30 km apart by road, so a rental car day could cover both. Without a car, pick one. A note on Furano and Biei: the lavender fields are 120 km northeast and technically day-trippable by seasonal JR Lavender Express, but you'll spend four hours on trains for three hours on the ground. Stay overnight there if you go.