I wholeheartedly disagree we need a NTR content warning in the game, because one of the main aspect of NTR is the exploratory aspect and the surprise element.
Furthermore, the main focus of the game is ghost-hunting, and the NTR aspect is just part of the story plot. Placing NTR disclaimer would only mislead players to perceive this game is a NTR-focused game in the first sight. Players only need to know this is a ghost-hunting game, adding any other unnecessary wordings would only confuse everyone.
It's like watching Goblin Slayer, if the audience saw there's a "Rape disclaimer" before the show starts, they will wrongfully thought Goblin Slayer is a hentai anime. But its not a hentai anime, its a fantasy anime about goblin-hunting, but also includes rape scenes. Wrongfully adding disclaimers will only mislead the audience.
It's unfortunate that western audience has a terrible culture of selfishly demanding authors/developers, to add something in a story that the author/developer doesn't wish to add.