50,000 years ago, Hell was destroyed because of too much Foul from the resentment of the souls that later turned to Soul Eaters and devoured everything in their wake, leaving nothing of Hell. The gods above in Heaven, in order to take care of the newly-died souls, created the Afterlife Department comprised of grim reapers. Huo Ling was delivering food that day when he met Yi Bing and the guy gave him a warning. When he arrived to the customer's unit, he was killed. Huo Ling: you set up a death flag for me! Yi Bing: I'm a grim reaper. I'm the flag myself. Let me help you solve the mystery of your death. Huo Ling: your sister! Alternative title: The Different Ways I Died at 23 Update: daily
This felt like a dream to them, but only the ones alive can dream and not them, those who are already dead. However, that doesn't stop them from feeling happy. After all, they highly respect Yi Bing. It is not wrong to say they idolize him, since Yi Bing is them, the grim reapers', progenitor.
The first time they met Yi Bing is when they became senior grim reapers. Yi Bing is someone you won't easily meet. That time when they met him, Yi Bing's assignment, a soul, had just finished its nine cycles and chose to continue reincarnating within its 81 lives. Yi Bing felt dejected because he really hoped his assignment to become a grim reaper, since the Afterlife Department lacks talents the most.