Travelling to Cape Soya
“Cape Soya is the northernmost point of Hokkaido, and therefore of Japan. Near to the city of Wakkanai, the cape is a popular stopping point for bikers and tourists, and has quite a few monuments, gift shops, a windmill and lighthouse. If the weather is good you can see Sakhalin, a Russian island once part of Japan, from the lookout point.
You can reach Wakkanai, the nearest city, by road, rail and air. From there, access to the cape is by bus, car or taxi.
Trains to Wakkanai start in Sapporo, and there are flights from both Sapporo and Tokyo to the city as well. From Wakkanai you can take a bus or drive the 31 kilometers to the cape along route 238 or take a taxi. A bus ride takes about 45 minutes.”
https://www.japan.travel/en/spot/1887/
(Japanese National Tourist Office)
Possible route from Fukuoka to (close to) Cape Sata
Kyushu by bicycle: Love hotels, hot springs and rugged climbs
(Japan Times)