In order to complete the Torii Gate in the game, you need to finish 4 construction phases, as it usually happens with Treasure Isle relics. In order to complete them, you need different amounts of the following materials:
– Metal
– Glue
– Aqua Vitae
– Fire
– Dye
Once completed, the Torii Gate will give you a boost (permanent) of +3 energy for treasure hunting. Which is great, combined with the same boost from the Hot Spring.