Mr. Yin and I really saw whether the deceased lived in the underworld.

Don't believe it. Even if he could, he wouldn't dare tell you. Believe what he said or not depends on your judgment. I believe that death is the suffering of the living and the next reincarnation of the dead. Live well if you live, and die if the other person dies, with no attachments. Don't let your helplessness stain the path of the other person's reincarnation.