Wan first met Raava when he saw her fighting Vaatu in the Spirit Wilds. Wan yelled at them because a lot of animals were in danger but Raava told him to go away but the fight does not concern him. However, Vaatu tricked Wan into firebending at them and separating them. Raava yelled at Wan for being tricked and informed him of the consequences of his actions. Later, when Wan was visiting the air Lion Turtle, Vaatu arrived and the residents asked why the two spirits were separated. Raava then arrived and told everybody to ask Wan, who explained that he was tricked.
Wan wanted to travel the world to collect elements so that he could try and amend his mistakes, but when he tried to gain airbending, he found out that he would need Raava's help to bend more than one element. Raava was still angry with Wan and initially refused to help him, but Wan convinced her to do so when he insisted on fixing his mistakes. Raava was concerned for Wan's well-being because merging to change elements was dangerous for him, but Wan insisted on trying and he ended up being okay.
Raava explained that the final battle between her an Vaatu would take place in a year so Wan was determined to gather more elements so that they would have a chance. Eventually, they had another run-in with Vaatu which severely weakened Raava. She was so small that Wan picked her up and put her in a teapot to carry her. Raava finally admitted to Wan that she previously looked down on humans but learned that they were capable of selflessness and bravery. As they were heading to the final battle, Raava was feeling hopeless about winning but Wan tried to reassure her that they still had a chance.
During the battle, Vaatu was easily overpowering Wan and thrashing him around. Wan and Raava fused but it still was not enough. Raava told Wan that she needed to leave Wan's body or he would die but he insisted that she stay. When Harmonic Convergence started, Wan used its power to permanently fuse with Raava. Raava informed Wan that they were combined for good and Wan was easily able to overpower Vaatu and seal him in the Tree of Time. Wan decided that it was now his duty to use Raava's light spirit to bring balance to the world. However, when he was much older, Wan was mortally wounded on the battlefield. He lamented that he failed to bring balance to the world but Raava told him that they would be together throughout all of his lifetimes and that they would never give up.
Waava is a very popular ship in the Legend of Korra fandom. Many love this pairing because of the fact that they permanently fused and that Raava said that they would be together throughout all of Wan's lifetimes. A lot of fans like to portray Raava in a humanoid form. Some do so to make Wan and Raava seem more similar. Some fans only ship Waava as an emotional ship due to the fact that they are permanently fused and cannot touch each other. While there are many different ways that this ship is portrayed, Waava is very popular.