A cikin 1954, jiragen ruwa guda biyar, ciki har da Tōya Maru, sun nutse a cikin Tsugaru Strait a lokacin guguwa, inda suka kashe fasinjoji 1,430. A shekara mai zuwa, Jirgin kasa na Japan (JNR) ya hanzarta binciken ramin. Har ila yau, damuwa ta kasance da karuwar zirga-zirga tsakanin tsibiran biyu. Tattalin arzikin zirga-zirga ya ga matakan zirga-zirga a kan Seikan Ferry da JNR ke sarrafawa ya ninka zuwa fasinjoji 4,040,000 / shekara daga 1955 zuwa 1965, kuma matakan kaya sun ninka sau 1.7 zuwa tan 6,240,000 / shekara. Hasashen ƙididdigar zirga-zirgar tsakanin tsibirin a 1971 ya yi hasashen karuwar damar da za a yi a ƙarshe ya wuce na tashar jirgin ruwa ta tsibirin, wanda aka yi hasashen yanayin ƙasa a cikin 1971. Tambaya: Menene aikin jirgin ruwan ya yi?
Ƙara girma wanda zai ƙare ya wuce damar da ke cikin tashar jirgin ruwa