First, draw the outline of the head and face. Then, focus on the beard - make it thick and maybe a bit wild. For the expression of anger, give the eyes a fierce look and a scowl on the lips. Add some shading to enhance the mood.
It could strain their relationship significantly. Naruto might start to distance himself from Kakashi, not trusting him as much as before. This could lead to a breakdown in their communication, which was previously a key part of their bond.
In the fanfiction, it could be that Kakashi is being too hard on Naruto during training. He might be pushing him beyond his limits without proper explanation or support, causing Naruto to feel frustrated and angry. Naruto is a determined character, but everyone has their breaking point.
The plot could be that Naruto gets a special mission to protect Kakashi's face from a group of rogue ninjas who want to steal Kakashi's identity. Naruto has to use his unique skills to fend off the attackers and keep Kakashi's face safe.
A possible plotline could be that a new enemy targets Kakashi because of his distinct face features, believing there is some hidden power in his appearance. Naruto then has to protect Kakashi. Another plotline could be a magical spell that gets cast on Kakashi's face, changing his expressions uncontrollably, and Naruto tries to find a way to break the spell.
Some fanfictions might introduce new, original villains. For example, a dark sorcerer - type character who wants to use Naruto's unique chakra for his own evil purposes. Kakashi has to face this sorcerer and his minions to keep Naruto out of harm's way.
Well, for starters, Kakashi has to deal with Naruto's hyperactive and sometimes reckless behavior. Naruto often acts without thinking, which could put him in danger. Sasuke, with his complex emotions and the burden of his clan's massacre, is also a handful. Kakashi needs to make Sasuke understand that revenge is not the only way forward. Additionally, Kakashi has to ensure that both Naruto and Sasuke get along well with each other. There could be rivalry between them, and Kakashi has to manage that in a way that doesn't harm their relationship or their growth as ninjas.