Perhaps Sasuke, being the proud Uchiha, tries to hide his concern at first. But the other villagers notice and start to nudge him towards Naruto. When he finally goes to see Naruto, he finds that Naruto is still as upbeat as ever despite being sick. This makes Sasuke respect Naruto even more, and he decides to stay with Naruto throughout his illness, and they end up having a stronger bond after Naruto recovers.
One idea could be that Sasuke, despite his usually stoic nature, feels a sense of worry when he hears Naruto is sick on his birthday. He could visit Naruto and bring him some traditional Uchiha herbal medicine that he secretly prepared. This would show a soft side of Sasuke and also deepen their bond in the fanfic.
The fanfic could explore how Sasuke deals with his emotions when Naruto is sick. He might be conflicted between his old rivalry feelings and his newfound, deeper feelings for Naruto. Sasuke could also be the one to stay by Naruto's side when everyone else is busy. He'd watch over Naruto while he sleeps, and when Naruto wakes up, there could be a moment of intense eye - contact that shows the unspoken bond between them.
Sasuke could play a crucial role. He might use his Sharingan to detect what's wrong with Naruto more accurately. Then he could go on a mission to find a special cure.
A 'Happy Birthday Sasuke' Naruto fanfic could be about Naruto planning a surprise birthday party for Sasuke. He might gather all their friends from the village, like Sakura, Kakashi, and Shikamaru. They could decorate Sasuke's old house with symbols of his clan, the Uchiha crest perhaps. Naruto would also make sure to have Sasuke's favorite food, tomatoes, available in abundance. It could be a story full of friendship and nostalgia, showing how much Naruto values Sasuke.
Yes, there might be such fanfics in the vast Naruto fanfic community. However, these often deviate from the original story's canon. Fanfics are a creative space for fans to explore different scenarios, but they can vary greatly in quality and adherence to the characters' original personalities.
In many such fanfics, Naruto's character often becomes more vulnerable yet also stronger in a different sense. His pregnancy makes him rely on Sasuke more, but at the same time, he is determined to still be a great ninja. Sasuke, on the other hand, becomes more nurturing. He steps up to protect Naruto and the unborn child, showing a side of him that was not as evident before.
One possible plot could be that Sasuke has been away on a long mission and has forgotten his own birthday. Naruto, who has been keeping track, decides to bring the celebration to him. He travels to where Sasuke is and with the help of some local people, arranges a small, intimate party. They share stories of their adventures and Naruto gives Sasuke a new headband as a gift, one that represents their combined journey.
Naruto would likely become more stable. With Anko as his adoptive mother, he'd have a stronger support system. He might be less impulsive as he has someone to guide him. Sasuke, on the other hand, could start to open up more. His cold exterior might soften as he experiences Anko's love and care. He could also learn to trust others more easily.
At first, it would be really awkward. Naruto might be all over the place, trying to make the best of the situation, while Sasuke would be cold and distant. But as time passes, they would start to communicate more. Naruto's positive attitude might slowly break down Sasuke's walls. They could start training together again, like old times, but with a new layer of closeness. Eventually, they might develop a deep respect and love for each other that goes beyond friendship.
The story could develop in a very dark direction. Sasuke might be filled with regret immediately after killing Naruto. This could lead to him isolating himself from the rest of the ninja world as he grapples with his actions. The ninja villages might be in chaos as Naruto was seen as a symbol of hope. Without him, there could be power struggles among different groups.