If Naruto got the Death Note, it would be a complete chaos. Naruto has a strong sense of justice, but his understanding of it is very different from Light's in Death Note. He might initially be horrified by the power of the Death Note and try to destroy it. However, if he decided to use it, he could potentially target powerful enemies like Orochimaru or Pain without having to engage in direct combat. But this would also corrupt his ninja way as killing without a fair fight goes against his beliefs. He would likely struggle with the moral implications throughout the story.
Naruto would likely face an internal conflict. His normal way of dealing with problems is through hard work, training, and believing in his friends. But the Death Note offers an easy way out, a way to kill without a fight. This would make him question his values. For instance, he might wonder if it's okay to use it on someone like Pain, who caused so much destruction in the village. On one hand, it could save many lives in the future, but on the other hand, it goes against his basic ninja beliefs.
Ryuk would probably just be amused. He is a Shinigami who has seen a lot in his existence. Fanfiction is just another strange human creation to him. He might chuckle at some of the more outlandish ideas in the fanfictions, like a character having superpowers beyond the Death Note.
Misa would likely be excited. She is a big fan of Light and the whole 'Kira' concept. In fanfiction, if there are scenarios where she has more power or a closer relationship with Light, she would be all for it. However, she might also get jealous if there are other female characters getting too close to Light in the fanfictions.
Oh, for sure! Death Note is considered a masterpiece in the manga world. Its unique concept and the way it unfolds make it a must-read. The characters' development and the moral dilemmas presented make it stand out from the crowd.