Well, it could be that he ate some bad ninja food. Maybe he ate a spoiled ration from a mission. You know, in the world of Boruto, they might not always have the freshest supplies on long missions.
Another possibility is that he was poisoned during a fight. His enemies could have used some kind of toxin that affects the stomach. In the Boruto universe, there are all sorts of sneaky ways enemies can attack. It could start with a tummy ache and then lead to more serious symptoms if not treated.
In the fanfic, it might be due to a ninja technique gone wrong. For example, if he was trying a new jutsu that affected his internal chakra flow and it ended up giving him a tummy ache. This could be a really interesting plot point as it shows the risks of experimenting with new powers.
Well, it could be about Corrin eating something bad. Maybe they ate some strange fruits in a forest and then got a tummy ache. The story might focus on how they deal with the pain, like trying to find a herbal remedy.
It could also be that he ate some magical food that didn't agree with him. For example, he might have tried a new kind of magical sweet from Honeydukes that had a strange side effect on his digestive system. Another reason could be that he was under a minor curse. Some of the dark wizards or witches in the story might have cast a spell on him that caused his stomach to ache as a form of petty revenge or to distract him from something important.
There could be many reasons. Maybe she ate something bad like spoiled food. It could also be due to stress or anxiety which can often affect the stomach.
For example, there's a girl called Sophie. She got a tummy ache. In her mind, her tummy was a kingdom. The cause of the pain was a dragon that was breathing fire and scaring all the good little creatures in the kingdom. A hero in shining armor came, fought the dragon, and once the dragon was defeated, Sophie's tummy ache went away.
The rest of his friends would probably gather around him, offering support and trying to cheer him up. They'd bring him water or whatever they thought might make him feel better. They'd also share stories to distract him from the pain, like the time they had an adventure together and overcame a difficult obstacle.
Sakura might immediately start trying to diagnose him. She is a medical ninja after all, so she'd be all business, checking his symptoms and trying to figure out what's wrong.
She can try drinking some warm water or herbal tea. It can soothe the stomach.
In this fanfic, a possible cause for Naruto's heart attack could be a hidden genetic defect. Maybe it was passed down from his parents or some sort of unknown bloodline trait that suddenly manifested. It could also be that he was exposed to a strange and powerful chakra that his body couldn't handle and it affected his heart negatively, causing it to malfunction and leading to a heart attack.
Ryder would definitely be the first one to help. He's the leader and he always takes care of the pups. He might have some special medicine in his pup - pack. Also, Skye could be helpful. She could fly around to find something to ease Chase's pain, like a cool breeze might make him feel better. Rocky could also use his recycling skills to make a special tummy - ache - relieving device out of old parts.