Actually, the best way to prevent Tanoyu Kyou from leaking information is to get her on board as well.
Once she dares to reveal the matter between Su Chen and Minako Ozawa, it would be tantamount to exposing herself.
If this comes to the Buddha's knowledge, the consequences...
She was clear about it.
Although she had not arrived at the villa when that woman was punished, she had heard plenty about the woman's tragic fate.
In the end, she was even cemented and sunk into the sea.
The possibility of dying here and now or dying later is something even a fool knows how to choose.
Originally, when Minako Ozawa took the risk alone, she was very afraid inside.
Now with Tanoyu Kyou's involvement, even if she were to die, there would be someone to back her.
Besides, her relationship with Tanoyu Kyou was the best.
In a place full of intrigues, where one might not survive the slightest misstep, it's always good to have one more ally.