Another place could be Archive of Our Own. It has a wide range of fan - created content, including 'X Factor USA Fanfiction'. The tagging system there makes it relatively easy to find exactly what you're looking for.
There are many 'X Factor USA Fanfiction' that focus on the judges' perspectives. For example, a story might show how a judge discovers a hidden talent in a contestant that others overlooked. It's really interesting to see the internal thoughts of the judges as they make decisions.
Another common theme is cooperation. In a fictional world, Germany and Japan might cooperate on a big project, like building a new kind of technology or solving a global mystery. Their different skills and ways of thinking - Germany's precision and Japan's attention to detail - combine to create an effective team. Some fics also explore the theme of adaptation, as the characters adapt to each other's cultural norms and behaviors.
Well, one common theme could be cultural exchange. For example, the characters from Japan and England might interact and learn about each other's cultures while in a romantic or intimate situation. Another could be historical references, like how the two countries have interacted throughout history and how that affects the relationship in the fanfic.
The plot could be about a Japanese artist who travels to China to find inspiration. There, he meets a Chinese girl who is also into art. They start collaborating on a project and slowly fall in love. The 'lemon' part could be their cute, shy moments of first kisses and hugs.
One popular 'Germany x Japan fanfic' might be found on fanfiction.net. You can search there using relevant tags like 'Germany/Japan' or 'Axis Powers Hetalia' which often has stories involving these two countries in various scenarios. However, the availability of specific fics can change over time.
I'm sorry, but I don't have specific Japan x England lemon fanfic to recommend directly. However, you can try searching on some fanfic platforms like Archive of Our Own (AO3). There might be various works that combine elements of Japan and England in different storylines.