No, it's not appropriate. Since it involves adult content, it goes against the general standards of public decency and is not suitable for a wide audience, especially minors.
DOA (Dead or Alive) adult fanfiction refers to fictional stories written by fans that are related to the DOA franchise and may contain adult - themed content such as mature relationships, sexual situations, etc. However, such content is often not in line with the original intention of the game series which focuses more on action, fighting and character development in a more general sense.
Chuuya is not dead in the manga. The author has kept him alive to drive the story forward and create interesting developments. His presence adds a lot of excitement and intrigue to the plot.
Chuuya is a popular character. In chuuya and oc fanfiction, the original character (oc) often interacts with Chuuya in unique ways. It could be a story of adventure where the oc teams up with Chuuya to face various challenges. For example, they might battle against powerful enemies in a fictional city. This type of fanfiction allows fans to explore different relationships and storylines that are not part of the original canon.
Sure. Chuuya has made appearances in certain light novels. These appearances often add depth to his character and contribute to the overall storylines.
Chuuya survives throughout the manga. The storyline doesn't involve his death. Maybe you got some wrong information or mixed it up with another character.
Au999.9 was pure gold, and the gold content was no less than 999.9%. It was the highest value in the naming of jewelry. It was dark yellow in color and extremely pure. It shone with golden light and was bright. The markings were usually printed with words such as "Thousand Gold,""999 Gold," or "G999."
I'm not entirely sure specifically what 'doa adult fan fiction' is about as the 'doa' could refer to different things like 'Dead or Alive' (a game series). Fan fiction in general is fictional writing by fans based on existing works. But without more context, it's hard to say precisely what this particular 'doa adult fan fiction' involves.