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 ya ninka sau 1.7 zuwa tan 6,240,000 / shekara. Hasashen zirga-zirgar jiragen ruwa tsakanin tsibirin a 1971 ya yi hasashen karuwar ci gaban da za a yi a ƙarshe ya wuce ƙarfin jirgin ruwan.
karuwar zirga-zirga tsakanin tsibiran biyu