There's also a possibility that it's Trish. She could be calling to warn Dante about a new threat that she has discovered. Dante would trust her information and start to make preparations to face this new danger.
Well, in the fanfiction, perhaps it's a call from an old friend who needs his help. Dante might then gear up and set off on a new adventure to assist his friend.
There's also a chance that it could be a new superhero or villain. Maybe a new hero wants to team up with Spider - Man or a villain is taunting him, starting a new plot in the fanfiction world. This would create an exciting situation for Peter to deal with while trying not to blow his cover in class.
Maybe it's a family member. For example, his sister could be calling because she needs his help with something urgent at home.
Perhaps it's his best friend who has some juicy gossip to share. But it's really bad timing as he's in class. His friend might not be aware of his class schedule.
In some cases, Dante could distance himself from Nero for a while. He might go off on his own to cool down and think things through. Meanwhile, Nero could be left feeling guilty or confused about why Dante got so angry.
It could be his friends from his secret group. They might be in some kind of trouble and need his help right away.
One possible reason could be Nero's over - eagerness or recklessness. Maybe Nero keeps getting into dangerous situations without proper planning, and Dante, being more experienced, gets pissed off at Nero's lack of caution.
Vergil is another character that would make the fanfiction more interesting. He has his own complex relationship with Dante and Sparda. His presence could add a layer of family drama. For example, he might be jealous of the time Dante gets to spend with Sparda, or he could try to prove himself to Sparda in a different way than Dante does.
Danny is extremely powerful as a half - ghost. His powers are based on ectoplasm and he has a wide range of abilities that make him a formidable opponent. However, Dante has been trained to fight demons all his life. He has strength, speed, and agility, as well as a vast knowledge of different types of demons and how to defeat them. If they were to face off in a straight - up fight without any environmental factors, it would be a close call. Danny's powers are more supernatural in nature, while Dante's are more combat - based. So, it's really hard to say who would be stronger.
Sure, it's very likely that such a fanfiction exists. Given the popularity of both Naruto and Dante, fans are always eager to create unique crossovers. In a 'naruto is dante fanfiction', one could imagine Naruto having some of Dante's abilities or characteristics, or perhaps they are in the same world facing common enemies. But keep in mind that the availability and popularity of such a fanfiction would depend on the fan community's interest in this particular crossover.