Sure. You can find them on various fanfiction websites. Look for ones that have high ratings and good reviews. Some might focus on crossovers where the characters from Death Note interact with those from My Hero Academia in unique scenarios. It could be a hero from My Hero Academia trying to stop someone misusing a Death Note - style power, or a Death Note character being influenced by the hero - centric society in My Hero Academia.
A popular plot is the 'transfer of power'. Imagine if a Death Note somehow made its way into the My Hero Academia world and a hero or villain got hold of it. They would then have to figure out how to use this new power within the context of their existing powers and the society they live in. Another plot is the 'moral dilemma' plot. A character, whether a hero or a villain, is faced with the choice of using the Death Note for what they believe is right, but they have to deal with the consequences and moral implications, much like Light did in Death Note.
They can be blended by borrowing the concept of intelligence and strategy from Death Note. In My Hero Academia, many battles are physical, but if we incorporate the strategic thinking of Light Yagami from Death Note, it could add a new dimension. For instance, a character could plan out their moves against villains not just based on their quirks but also on out - thinking them like Light did. This could lead to more cerebral battles in the My Hero Academia universe. Also, the idea of a hidden identity, which was crucial in Death Note, could be introduced. A hero could have a secret identity that they use to fight crime in a different way, similar to how Light hid his identity as Kira.
First, familiarize yourself with both universes thoroughly. Know the characters, their powers, and the rules of each world. For example, in Death Note, the rules about how the Death Note works are crucial. In My Hero Academia, it's about the Quirks. Then, come up with an interesting concept that combines the two. It could be something like a character from My Hero Academia getting a Death Note and how that changes their view of heroism.
Overall, the Death Note Christmas comic could be a festive spin-off that maintains the dark and mysterious tone of the original series while adding holiday elements. It might explore new aspects of the characters' interactions during the Christmas season.
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.