Well, I really like 'The Magic of the 10 Kingdoms' fanfiction. It delves deep into the magical aspects that are often overlooked in the original concept. The way it describes how magic works in each of the 10 kingdoms is fascinating. Then there's 'The Rebellion in the 10 Kingdoms'. This one shows the political unrest and power struggles within the kingdoms. It's a great read if you're interested in the political side of the 10 kingdoms. Also, 'The Friendship in the 10 Kingdoms' is a heartwarming story about how different characters from various kingdoms form strong friendships.
One great 'Tears of the Kingdom Fanfiction' is 'The Adventure Beyond Hyrule'. It takes the characters on a journey outside the known boundaries of Hyrule. The author does an amazing job of keeping the personalities of the game characters intact while introducing new and exciting challenges.
One great 'Kingdom Hearts Crossover Fanfiction' is 'Kingdom Hearts and Final Fantasy: The Convergence'. It combines the elements of Kingdom Hearts and Final Fantasy in a really interesting way. The characters from both universes interact in a believable manner, and the plot keeps you hooked from start to finish.
You can begin by playing the first game in the series. It sets the foundation for the entire Kingdom Hearts story, introducing the main characters like Sora, Donald, and Goofy, as well as the concept of the Keyblade. The first game also starts to unfold the mystery of the Heartless and the different worlds that are connected in this universe.
I really like 'Bleach - Kingdom Hearts: A New Alliance'. It has an interesting take on how the powers from both series would mesh. For example, it shows how a character from Bleach might use a Kingdom Hearts - inspired weapon in a creative way. The story also delves into the backstories of some characters more deeply, which adds a lot of depth to the fanfic.
Since it's a graphic novel about a hidden kingdom, it might involve elements of mystery. There could be a mystery surrounding the existence of the kingdom, or perhaps something within the kingdom that needs to be uncovered. It might also tell the story of different groups or factions within the kingdom, their relationships, and how they interact with the outside world or the main character who has entered their domain.
There are also some specialized light novel websites. For example, BookWalker is quite popular for light novels. It has a large catalog and you may be able to find 'Kingdom' there. However, make sure to check the legality and terms of use in your region.