One possible reason could be that Naruto is feeling lonely. Despite having friends, he still has moments when the weight of his past, like being an orphan and ostracized in the village as a child, hits him hard. Jiraiya might see Naruto crying because of these memories resurfacing.
It can be a good sign. Watching stories can expand the daughter's imagination. And if the boyfriend is open - minded, he can join her and they can have some interesting discussions about the stories, which is beneficial for their relationship building.
Maybe Harry is crying because he misses his parents. He often feels the pain of their absence deeply, and in this fanfic, when Sirius sees him, that could be the cause.
Sakura may react with a sense of urgency. She would drop whatever she was doing and rush to Naruto's side. She'd be worried that something truly terrible has happened. If Naruto is hesitant to talk, Sakura might just sit quietly with him, waiting for him to open up. This would show her patience and understanding, and also how much she values Naruto as a friend.
The plot might involve Naruto crying due to a misunderstanding with his friends. Kakashi witnesses this and steps in to mediate. He first calms Naruto down and then arranges for Naruto and his friends to have an open conversation. During this process, Kakashi shares some wisdom about friendship and communication, helping them resolve their differences.
Cedric might immediately go to find someone who is closer to Harry, like Hermione or Ron. He realizes that they might be better at dealing with Harry's emotions, so he fetches them to come and comfort Harry. This shows Cedric's understanding of Harry's relationships and his concern for Harry's well - being.
Jiraiya would probably offer some words of wisdom. He has a lot of life experience, so he might tell Naruto that crying is not a sign of weakness but a way to let out pent - up emotions. For example, he could say something like 'Boy, those tears are like the rain that nourishes the seeds of your growth.'
She might immediately go to comfort him. Hinata has always cared deeply for Naruto, so seeing him cry would likely trigger her protective and empathetic side.