The pairing of L and Misa is interesting because they are such different characters in the original 'Death Note' series. L is highly intelligent and logical, while Misa is more emotional and impulsive. In fanfics, seeing how these two contrasting personalities interact and potentially develop feelings for each other is fascinating.
I really liked 'The Unlikely Bond'. It's a fanfic that starts with L being intrigued by Misa in a way he didn't expect. The writing is quite engaging as it shows how their interactions gradually change from suspicion (as in the original series) to a sort of understanding and then something closer to affection. It's a slow - burn story that is really enjoyable to read.
L's death in the manga occurs as a result of Light's elaborate schemes. Light finds a way to trick L and eliminate him, marking a significant turning point in the story.
Their relationship could be developed with more trust. In the original, there was a lot of manipulation. But in fanfiction, they could start being honest with each other from the beginning, sharing their true thoughts and feelings, which would lead to a more stable and loving relationship.
One idea could be a story where Light and Misa try to navigate their relationship outside of the Kira case. Maybe they go on a trip together and have to deal with normal couple problems while still being on guard against possible pursuers who might suspect their true identities.
One possible plotline could be the shock and confusion among the other characters. Since L's pregnancy is so unexpected, it could disrupt the power dynamics in the story. For example, Light might try to use this situation to his advantage in their battle of wits.