The journey to the north pole was hard for Aang. In more ways than one. For the entire trip, Aang was sitting next to his dream girl, but was afraid to tell her. His only relief was his hand, and the occasional celebrity sex he would get in some places that he visited. He is the avatar after all. Many people were happy to see him return. However, Katara seemed not to care, she only thought of him as a brother.
As they arrived at the North Pole, Aang began his waterbending training, although he did tend to goof off quite a bit. Yet, as the days went on, he progressed rapidly. He was becoming quite a bender. While watching this, and being upset that she could not be taught bending herself, Katara grew interested in Aang. She started to find ways to be around him, much to the simultaneous enjoyment and disappointment of Aang. Eventually, after a long day’s bending, Katara decided she had to try something to both learn to bend, and satiate her desires.