Naruto and Sasuke have known each other since they were young children as both they were born in the same year and attended the ninja academy together. Sasuke was popular and at the top of his class which made Naruto jealous. He was also popular with the girls including Sakura Haruno whom Naruto ended up having a crush on. Naruto and Sasuke had a huge rivalry during their years in the academy. At one point, when Naruto was angrily staring into Sasuke's face, another student accidentally pushed him over and the two kissed by accident.
After graduating from the academy, Naruto and Sasuke were placed on the same team under the leadership of Kakashi Hatake along with Sakura. This somewhat inflamed the love triangle that already existed. Naruto was determined to surpass Sasuke and after developing more skill, the latter started to grow jealous. Because of this, he decided to leave the village in order to go train under Orochimaru. Naruto attempted to stop him and the two ended up having a fight. Sasuke admitted that Naruto was his best friend and eventually won the battle. Naruto swore that he would still bring back Sasuke one day.
Over two and half years later, Naruto and Sasuke were reunited again. Sasuke was much more merciless this time and was still able to best Naruto in battle. The rest of the village started to give up on him and Sakura tried to convince Naruto to do the same but he refused to give up. The two later met again during the fourth war and Sasuke decided to protect the village after learning the truth about his brother Itachi. Both fought side by side just like old times.
Naruto and Sasuke later spoke to the sage of six paths and found out that they were the latest reincarnations of Asura and Indra who had a serious conflict. After defeating Kaguya, Sasuke resolved to destroy the Kage and Naruto was forced to fight him once again. Naruto managed to win the battle and finally resolved their issue. Thanks to the influence of the latter, Sasuke's status as an international criminal was cleared. The two would remain good friends and their families also ended up being close.
SasuNaru is very popular from the start of the series and was gaining more fans over time, and is currently one of the largest shipping fandom of Naruto. It is also common for people who ship SasuNaru to also support NaruSasu, KibaHina, LeeSaku and many more. It most commonly rivals the NaruHina, NaruSaku, and SasuSaku ships.