It's hard to say for sure. The availability of Venti in the story depends on multiple factors such as the story's genre, setting, and the author's intentions. It could be possible, but you'd have to look closely at the story's details to know for sure.
Often, in Himiko x Kokichi fanfiction, the setting plays a crucial role. If it's set within the context of their original world, the power dynamics and the overarching plot of that world can influence their relationship. Maybe they team up to face a common enemy, and during this process, their feelings for each other gradually develop. Their interactions can be filled with banter, like Kokichi teasing Himiko about her spells not always working as expected.
In 'kokichi snaps fanfiction', it may also be related to the overall theme of the original work where Kokichi is from. If it's from a game, perhaps the events in the game lead him to a point where he can no longer hold back his true self or emotions. The fanfiction could be a way for the author to expand on that moment and show how it impacts the surrounding characters and the story world.
Yes, you can get Venti from the story. In the game's story, Venti is a key character. His story is intertwined with the lore of Mondstadt. For example, his role as the Anemo Archon is revealed through various quests. These quests show his connection to the city, its people, and the overall history of the region. He has a carefree yet mysterious personality, and his actions in the story often have a significant impact on the events that unfold in Mondstadt.
Well, in a Venti identity reveal fanfic, it could involve Venti dropping his carefree bard facade and showing his more divine or ancient side. It might include scenes where he has to use his true powers to protect Mondstadt from a great threat. And this could lead to a whole new understanding of his character by the people of Mondstadt and the readers of the fanfic.