Why didn't Otani save the birds?

Because Otani has long been lost, he lives in a brand-new identity. Even many people don't know his true identity when they see Otani, so the bird unfortunately becomes a mouse and is almost drained of strength. According to the inquiry, after Otani's identity was exposed, in fact, for TPC, Otani has long since disappeared, and even Lena has been anonymous, but there is no guarantee of what will happen in the future. In addition, TPC happened to be holding a Mars immigration plan at that time, so Iruma Megumi took this opportunity to let Otani and Lena go to work on Mars in a brand-new capacity, and must not expose the fact that they are Diga again. Otherwise, you may never be able to live a normal life, and the process in the middle is tortuous, just because of director Zejing and even the hawkish Yoshioka who took care of Otani, Iruma Megumi was busy until he successfully saved Otani, but Bird obviously didn't have such resources. So Otani can't save the bird.