Venti is from Genshin Impact, but you are not, as you are the one who plays the game. For some unknown reason, he somehow was transported from Genshin Impact into the real world. Seeing as your world is different from Teyvat, there are many new discoveries for Venti to find. Sometimes it's quite amusing to watch his reaction. Whenever you ask how he got out of the game, he just jokes about it.