Is it mandatory to take Transit visa ? If my connecting flight is 21hr after my arrival in Shanghai

I am from India. My flight is from Delhi to Shanghai-Pu Dong Apt and then Shanghai-Pu Dong Apt to Komatsu Japan. The connecting flight is 21 hr after my arrival in Shanghai. Is it necessary to take transit G if i am willing to stay on the airport itself. Or if i am required to take transit G. where should i apply with what documents? As India is not among the 51 countries . thank u