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.
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.
For an OC in DOA fanfiction to be great, they should have well-defined powers or skills that are balanced and don't overshadow the existing characters. Their interactions with the canon characters should be believable and add depth to the story. Also, a distinct visual design helps them stand out.
First, check for updates. The game developers may have released patches to fix bugs, including those that might prevent the story mode from working. If there are updates available, install them. Second, make sure your network connection is stable if the game has any online components related to the story mode. A poor connection could cause issues.
One interesting doa fan fiction could be about the characters' backstories before the main events of the game. For example, a story exploring Kasumi's training days in her village.
There could be many possible fanfics about Christie and Bayman in DOA. It might involve their adventures together in the DOA tournament world. Maybe they team up against common enemies or have a friendly rivalry.
A prevalent theme is adventure. The stories usually involve Kasumi and the OC going on various quests or facing dangerous opponents. This gives the opportunity for exciting fight scenes and exploration of different areas in the DOA universe. Also, the theme of loyalty often comes up. The OC may prove their loyalty to Kasumi or vice versa during difficult situations.
One interesting crossover could be the characters from Naruto finding themselves in the world of DoA. For example, Naruto's ninja skills like his shadow clone jutsu could be used in the DoA fighting arenas in really unique ways. Maybe he'd team up with some DoA characters to fight against a common enemy.