La Santa Muerte is often associated with folk religion and has various beliefs and tales attached. Some see it as a protector, while others have different interpretations. It's a complex and diverse story.
One common theme is the exploration of their unspoken connection. Their relationship in the original work is complex, and fanfiction often dives deeper into it, like how they might support each other through their personal traumas.
Well, 'In the Garden of Eden' is a popular 'kaworu x shinji fanfiction'. It presents their relationship in a very idyllic and pure way. 'Under the Stars' is also worth checking out. It has a lot of heart - warming moments between them. And don't forget about 'The Silent Understanding', which shows how they communicate without words in a really interesting way.
In general, the Evangelion mangas are considered good. They expand on the anime's universe, providing more depth and character development. However, it depends on personal preferences as some might find the style or pacing not to their liking.