Happy might also become Luffy's friend. Luffy would be amused by Happy's flying ability and his cute appearance. Happy could also help Luffy navigate the Fairy Tail world, as he knows it well. And Luffy might share his food with Happy, which would make Happy very happy indeed.
It could be his dog. Dogs are often considered man's best friend, and in a story about a boy, a dog would be a very likely candidate. The dog could be loyal, always by the boy's side, and they could go on all sorts of adventures together.
It's also possible that the girl's best friend is an older person, like an aunt or a grandmother. They could have a special bond where the older person gives the girl advice and shares stories from her own life, and in return, the girl brings youth and energy into the older person's life.
Li Qin and Zhao Liying had the best relationship. The two of them had worked together many times, including in 'Dream of the Red Chamber' and 'Run! Brothers " and variety shows. They worked together frequently and had a lot of time and opportunities to interact. As a result, they had a deeper understanding of each other and became good friends. In addition, the interaction and tacit understanding between the two were also appreciated by the audience. The other search results didn't mention Li Qin's best relationship with anyone else.
Wang Hedi and Song Yiren had the best relationship. They became good friends during the filming of " General Night 2," and Song Yiren's lively extroversion gave Wang Hedi a lot of encouragement. When Wang Hedi was asked who his best friend was in the episode of " Fifty Miles of Peach Blossom Cove," he answered without hesitation that it was Song Yiren. Their friendship was considered sincere. Wang Hedi had even invited Song Yiren to be a guest on the show when he realized that she was in a bad mood, quietly accompanying her. Therefore, it could be said that Wang Hedi and Song Yiren had the best relationship.