Naruto died in the manga because he gave everything he had to ensure the safety and peace of his world. The battles were extremely demanding, and his body and chakra couldn't handle the strain anymore.
There could be a scenario where Naruto sacrifices himself to save Boruto or the entire Hidden Leaf Village from a catastrophic event like a massive attack by an unknown and dangerous force. He might use all his chakra to protect the village, leaving him with no energy to survive.
Uzumaki Kushina was one of the most important figures in Naruto. She was a ninja with the Eternal Kaleidoscope Shurakan and the leader of the Uzumaki clan. However, the cause of her death was still a mystery.
According to some information and speculations, Uzumaki Kushina might have been killed by her own Uchiha clansmen. In Naruto's storyline, the Uchiha clan had powerful eye magic abilities, including the Shura Eye and Amaterasu. These abilities could instantly lock onto and attack a target. During a battle with the Whirlpool Race, a member of the Uchiha Race used his eye-bloodline ability to try to kill the Whirlpool Kushina. However, due to the ability of the Eternal Kaleidoscope Shurakan, she was immune to this eye attack and ultimately protected herself from harm.
Another possible cause of death was that Uzumaki Kushina might have been killed by her lover, Naruto. In Naruto's storyline, Naruto and Uzumaki Kushina had a deep relationship. They had experienced many difficulties and challenges together. During a battle between Naruto and Uchiha Sasuke, Uzumaki Kushina was injured and died in order to protect Naruto.
No matter what the cause of death was, Kushina was an important Naruto character. Her death had a profound impact on the development of the story.
Another possibility in fanfiction is that Naruto succumbs to a deadly disease or poison. It could be a new, mysterious illness that the medical ninjas in the village can't cure in time, leading to his death.
Well, as of now, Naruto is still alive in the Boruto manga. There might be some intense battles and challenges, but no death for him yet. Maybe you got some wrong information?