It is called “Shichiri no Watashi” because the boat reached Kuwana no Watashi (port) from Netta・Miya no Watashi in Tokaido sailing about 27 km.
At that time, it was crowded as a 42nd post town of Tokaido.
“Shichiri no Watashi” which is the only sea route in Tokaido was drown a lot in ukiyo-e.
This big tori is called “The best Torii in Isenokuni” because visitors who come by sailing from Miya no Watashi enter Isenokuni here. And with rebuilding every 20 or 30 years of Ise Shrine, it is reconstructed.

【The site of TripAdvisor】
https://www.tripadvisor.jp/Attraction_Review-g651657-d1369482-Reviews-Remains_of_Shichiri_watashi-Kuwana_Mie_Prefecture_Kinki.html