Isahaya (Japan) and Shimonoseki (Japan) are 149 km (93 mi) apart in a straight line. The way we suggest is by train and ferry, via Shimabara, Kumamoto and Fukuoka: ~3h 55m door to door with 3 changes, for ~€19–73 per person. No flight is needed.
Step by step
Train from Isahaya to Shimabara: ~35m, 31 km, ~€2–8
Ferry from Shimabara to Kumamoto: about 45m, 30 km, ~€7–20
Train from Kumamoto to Fukuoka: about 45m, 92 km, ~€5–30
Train from Fukuoka to Shimonoseki: ~1h 5m, 62 km, ~€4–20
Every route we know
Train + Ferry + Train, via Shimabara, Kumamoto and Fukuoka: ~3h 55m, 3 changes, ~€19–73
Train + Ferry + Train + Ferry, via Shimabara, Kumamoto and Kitakyushu: ~5h 5m, 3 changes, ~€22–70
Questions
How long does it take to get from Isahaya to Shimonoseki?
~3h 55m door to door by train and ferry, via Shimabara, Kumamoto and Fukuoka, including time for changes.
How much does it cost to travel from Isahaya to Shimonoseki?
~€19–73 per person for the route we suggest. These are estimates from travel-guide prices and published tariffs, not quotes: check the operator for today's fare.
Is there a direct train from Isahaya to Shimonoseki?
Not that we know of: the routes in our data change via Shimabara, Kumamoto and Fukuoka.
Times are rough door-to-door times, with time to change included. A "~" marks a rough time worked out from the distance. We don't have timetables, and fares are rough estimates, not quotes: check Google Maps or the operator before you travel.