From the Start, I Sell Weapons in the Underworld

Xu Zian died unexpectedly, only to discover that the Black and White Impermanence had brought him to the underworld. Unwilling to live an ordinary life, he became an apprentice to the spirit of the Spirit Communication Tome. From then on, Xu Zian's life took an extraordinary turn.

With the tome's help, Xu Zian began selling weapons in the underworld.

Xu Zian has a spirit gun that can slay ghosts and kill gods, yet he has let someone down.