I think the masked man is either the emperor himself or a eunuch close to the emperor, acting under his orders to save Zhang Hai. Since the emperor doesn’t have an heir, he wants to prepare Zhang Hai to become the next crown prince and future ruler. Also, through Zhang Hai, he might be able to find the third person and the third bronze fish in order to unlock the Seal Orb.
I also believe that the third person is Zhao Bingwen, the Minister of Finance. He sent his daughter to live with Anto from a young age so she could spy on him. If you’ve noticed, Anto has been coughing and sick lately, and Zhao Bingwen’s daughter—who is a close friend of Anto—keeps bringing him medicine. I suspect they are planning to poison Anto slowly, just like how Zhuang Luyin’s wife killed Xiwan.
I also believe that the third person is Zhao Bingwen, the Minister of Finance. He sent his daughter to live with Anto from a young age so she could spy on him. If you’ve noticed, Anto has been coughing and sick lately, and Zhao Bingwen’s daughter—who is a close friend of Anto—keeps bringing him medicine. I suspect they are planning to poison Anto slowly, just like how Zhuang Luyin’s wife killed Xiwan.