Lines of red torii placed so close together they form a tunnel are a common sight throughout Japan. The most famous and most photographed are at the Fushimi Inari Shrine near Kyoto, but smaller versions can be found all over at shrines and temples.
They are usually made of wood, occasionally steel, but more often nowadays plastic pipe is being used. Each torii will have been paid for by a donation, and the name of the donor is usually written on each, similar to how some shrines will have lines of more expensive stone lanterns.
The top photo is from the Inari Shrine in the grounds of Suwa Shrine, Nagasaki. The second photo is at Tadaji Temple in Hamada. The third is a small Inari hokora near Kokura Castle.
The photo above is an Inari shrine in the grounds of the Hitomaro Shrine in Masuda.
If the Inari shrine is on a hillside, like at Fushimi, then the torii tunnels will switchback up the hillside like the photo above taken at the Taikodani Inari Shrine in Tsuwano.