The Hokkaido the Shinkansen forgets: three days down the Oshima Peninsula

The Hokkaido Shinkansen climbs under the Tsugaru Strait, surfaces in the south of the island, and stops. Almost everyone aboard is already thinking about Sapporo — the beer, the ramen, the snow two hours further north — and transfers onto a limited express without once looking south. Behind them the Oshima Peninsula (Oshima-hantō, 渡島半島) hangs off the map like a lobster's claw, and the fast train was never built to go there.

Where the fast train stops being fast

The Shinkansen terminates at Shin-Hakodate-Hokuto (新函館北斗), a station set among fields a short train ride from the city it is named for. You change there onto the Hakodate Liner to reach Hakodate (函館) itself, and that is where the rails toward the peninsula run out. The old Esashi Line, which once threaded down the western coast, closed years ago; the steel was lifted, and the way south is now a bus or a rented car. Check this before you build a morning around a timetable that no longer exists.

From Hakodate Station the buses leave for two different edges of the claw — Matsumae at the southern tip, Esashi on the western shore. Hakodate Bus runs both routes a handful of times a day, not every half hour, so the peninsula sets your pace rather than the other way round. Confirm the departures on the operator's own site the night before, because the last bus back can leave while the afternoon still looks open.

Matsumae, the castle at the end of the line

Matsumae (松前) holds the only Japanese-style castle on Hokkaido, and the northernmost in the country. The keep you see is a reconstruction, small and dark-timbered, standing where the Matsumae clan once ran the domain that controlled the island's trade — and the park around it is the real reason to come in spring. Matsumae Park is planted with hundreds of cherry trees across many varieties, early-blooming to late, so the flowering here staggers over weeks rather than a single frantic weekend; when Honshū has long dropped its petals, this hillside is still white and pink.

Below the castle, the old temple district (teramachi, 寺町) lines a row of wooden halls along a quiet slope, the kind of lane where you hear your own footsteps. Eat the pickle the town gave its name to: Matsumae-zuke (松前漬け), strips of dried squid and kelp cured with herring roe until the whole thing turns glassy and salt-sweet. You will find it in shops near the castle and on half the menus; prices and opening days shift with the season, so ask at the counter rather than trusting a sign.

The western shore, one slow road

The coast road between Matsumae and Esashi runs with the Sea of Japan on one side and low green hills on the other, through fishing hamlets where the boats outnumber the parked cars. Kaminokuni (上ノ国) and Assabu (厚沢部) are the sort of places the bus passes through rather than stops in, but Kaminokuni holds the earthworks of Katsuyama-date (勝山館), a medieval fortified trading post dug into the hillside, where excavation has turned up both Japanese and Ainu artefacts in the same ground. There is little English signage and no crowd; bring patience and a map you have saved offline.

This is the stretch where a rented car earns its cost, if you are comfortable on a two-lane coastal road. Without one, treat the shore as a single deliberate hop — one bus from Matsumae, or back up through Hakodate — and spend the saved hours standing still in one town rather than glimpsing three from a window.

Esashi, a herring town that remembers

Esashi (江差) was rich once, on herring — the fish ran so thick that merchants built mansions on it, and the folk song Esashi Oiwake (江差追分) still carries the swagger of that money. The town keeps a restored street called the Inishie Kaidō (いにしえ街道), where old merchant houses and a preserved residence or two let you walk into the plank-floored rooms where that trade was counted. Over the water sits Kamome-jima (かもめ島), a flat-topped island joined to the shore by a causeway and ringed by a walking path that fills an unhurried hour.

Climb to Ubagami Daijingū (姥神大神宮), the shrine the town treats as its oldest and its anchor. In August its festival pulls tall wooden floats through the streets for days, lantern-lit and loud in a way the rest of the calendar is not; if you come then, book a bed early, because the town fills. The rest of the year Esashi is quiet enough that the sea is the loudest thing you hear.

鰊（にしん）が去っても、町は歌を手放さなかった。

Getting there, and getting it right

Reach the peninsula by flying into Hakodate, or by riding the Shinkansen to Shin-Hakodate-Hokuto and transferring down to Hakodate Station; the buses for Matsumae and Esashi start there, run by Hakodate Bus. Build each day around their timetable, confirmed the night before on the operator's site, and assume the last return leaves earlier than you would like. Late April into early May is the window for the Matsumae cherries; August is the Esashi festival; deep winter turns the coast road grey and thins the schedules, so go knowing the season decides what is open.

The one mistake to avoid is treating this like a mainline day trip — arriving without a confirmed way back, expecting a train that was pulled up years ago, or trying to pin both Matsumae and Esashi into the same afternoon. Give each a night if you can. The peninsula rewards the traveller who lets it be slow, and quietly punishes the one who treats it as the stop before Sapporo.