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.
A friend of Corrin's, like a fellow traveler. This person could be by Corrin's side, offering support and comfort while Corrin is suffering from the tummy ache. They might also be the one who goes in search of help or medicine.
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.
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.
First, think about what could cause Coraline's tummy ache in the story. It could be the strange food in the Other World. Then, describe how she feels. For example, 'Coraline clutched her stomach as a sharp pain shot through it.' Next, plan out how she will deal with it. Will she ask for help? Maybe she'll try to find a cure on her own.
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.
Once upon a time, there was a little girl named Lily. One day, she had a terrible tummy ache. As she lay in bed, she started to have a strange fantasy. In her mind, her tummy was a magical land. The pain was caused by a naughty little goblin who was running amok and knocking over all the tiny houses of the friendly bacteria that lived there. Then, a fairy with a magic wand appeared. The fairy chased the goblin away and sprinkled some magic dust on Lily's tummy. Immediately, the pain started to fade and Lily drifted off to a peaceful sleep.
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.
One good 'Coraline tummy ache fanfic' could be one where Coraline eats something in the Other World that causes the tummy ache and then has to find a way to cure it with the help of the cat. It might focus on her journey through the Other World while feeling unwell.