The first time I knew Otani was a girl from Dijia, Shaji, a cosmic girl. She is not from the earth, but she has lived on the earth for many years, because she can't go back to her planet alone. It was not until humans dug up Machina that Shaji summoned Machina to take her home with a flute, but Machina was attacked by the victorious team and almost killed by Diga. Fortunately, Shaji told Machina's identity in time, and when he left, Shaji took action.
In episode 16, the Jinglong minefield, which once subdued ghosts, saw Otani's identity at a glance. He also said: Sir, you are not human. Fortunately, Otani has a good temper, or he will fight, but Otani in the human body is no match for Jinglong minefield. Jinglong, who once took it as his duty to subdue demons, was also the predecessor of Dagu. Finally, he told Dagu how to be a hero.
In the seventeenth episode, the alien monster "Blue Bull" Lei Deer also saw the identity of Otani. He also asked Dagu to play "Red Buff" ABBA Bath, and provided ABBA Bath's weakness. He successfully helped Dagu defeat ABBA Bath, and the human hijacked by ABBA Bath also returned to the earth, and Lei Deer also returned to his own planet. Finally, the grandmother who takes care of Lei Deer seems to see through the identity of her elder sister-in-law. She said meaningfully to her elder sister-in-law, "Is it impolite for you to call me grandma?" I doubt that grandma has seen through the identity of her elder sister-in-law, otherwise she would never say such a strange thing.
With the development of the plot, more and more people know that the elder sister-in-law is Dijia. In episode 44, scientist Masaki Keigo, Otani's girlfriend Lena, Captain Iruma Megumi and so on appeared until everyone knew that Otani was Diga Altman.