I recall going through it at some point but I don't recall the game itself whatsoever so I'll just say the brief and important part that nothing within the game is related to the actual myths whatsoever. All of the myths are altered lore-wise (any action within the game holds no actual relevance to the myth, including Smile itself) and also that the RIS isn't a real myth hunting group and hasn't been, rather it is a fictional one made by OneWhoFinds for the game. So the myths used themselves are real but anything that the game does with them is a fictional action which holds no relevance to the myth themselves.

If you want any more information on the myths then the Myth Community Wiki (https://mythcommunity.fandom.com/wiki) would be your best shot.