The development of side characters in Naruto was part of the primary charm. It pulls the audience in by keeping just the right balance between a character's personality, backstory, development, and relationships. Aside from being a story about war and superpowers, Naruto also depicts coming-of-age quite well throughout its runtime.
Multiple characters that were portrayed uniquely have grown to be someone reflecting on events from the past. Naruto grew into a Hokage and married the only girl that showed him constant support, while Sasuke reflected on his past doings and dedicated his life to supporting his family and village.
Amidst all of this, one such relationship developed into one of the best duos in anime. Shikamaru and Temari, despite being from different villages, fell in love with each other throughout the story's runtime in different arcs.
Shikamaru and Temari have one of the best-developed relationships in Naruto
Relationships between side characters are easy to theorize, solely because of things that get overlooked by either the author or the animation studio. There are already a lot of Naruto couples that do not make sense even today, or some that do, but fans cannot get behind.
However, one perfect relationship that gets backed by everyone is Shikamaru and Temari. Both of these characters were introduced as opposites, but they grew closer to each other as time and the world around them changed drastically.
Shikamaru was a calm and lazy individual who did not want to fight anyone, while Temari was introduced as someone who was capable of violence and insults towards those weaker than her. Her soft spot for Shikamaru came not because of his Jutsu, but because of his wit and calmness during a fight.
During the Chunin exam, Shikamaru completely outplayed Temari, making him the winner of the two strategists. Although Shikamaru did forfeit the match, Temari felt a sense of defeat for the first time after coming to the leaf village and was simply amazed by how competent Shikamaru was despite being lazy.
Temari's entire character during the early days of Naruto was based on being the arrogant one who eventually gets to know their place after being beaten up. However, that wasn't the case when she was defeated by Shikamaru. The latter did not humiliate her and did not care about anything except being free from work.
Temari's development as a character started to show when she fell for Shikamaru. She has been shown to support him in numerous ways ever since.
After the Chunin fight, Temari saw Shikamaru as someone special. During the Sasuke retrieval arc, she helped him in a fight against Tayuya and stayed to talk to him after several members of Konoha 11 got injured under his leadership.
Temari developed immense respect for someone like Shikamaru, which was very rare for someone like her. From being blinded by overconfidence and arrogance, to falling in love with one of the laziest shinobis, it is safe to say that Temari and Shikamaru's relationship exhibits more character development than silly romantic flirting.