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
Gu Shi looked at Yi Bing when he heard him asked. "Fortunately, Shou Ji and Shi Jiu are there to protect the other departments." He answered when they recalled that Shou Ji and Shi Jiu used some devices that Shou Ji asked his family in the interstellar world to protect the other departments from the enemies by setting up a barrier around the area.
Now that Gu Shi recalled it, it seems that Shou Ji and Shi Jiu also used a mecha earlier. Gu Shi's brow twitched and he noted down to remind them to return the mechas to the other world. One of the reasons for this is to not overindulge the technology of the Stable World or else the Stable World would not be a Stable World anymore.