It focuses on the story of L's early days and how he solves cases. In this novel, we see L's unique detective methods and his battle of wits against various criminals.
In 'Death Note Another Note novel', a major theme is the search for truth. The characters are constantly trying to figure out who is using the Death Note and for what purposes. There is also the theme of the thin line between justice and vengeance. Some characters may think they are dispensing justice with the Death Note, but in reality, it might be more about personal vendettas. This blurry line is explored throughout the novel.
Mello is quite an interesting character. His determination and his somewhat unorthodox methods make him stand out. He is willing to take risks and use his intelligence in creative ways to achieve his goals related to the Death Note.
One of the main themes is the battle between good and evil. Light, with the Death Note, represents a form of extreme justice that blurs the line between right and wrong. Another theme is the power of intelligence. Light and L constantly outwit each other using their brilliant minds. Also, it touches on the concept of morality. The use of the Death Note to kill people, even criminals, raises questions about who has the right to judge and take lives.
One possible fanfiction could be where Light is in the hospital due to an unexpected illness. Maybe he uses this time to plot his next moves in the Death Note world without arousing too much suspicion. He could be pretending to be weaker than he actually is while observing the people around him, looking for potential Kira supporters or enemies among the hospital staff and patients.