I'm a Messenger in an Infinite World

One day, an app called [Post Office] inexplicably appeared on Ai Cen's phone. The app told her to deliver letters.

She thought it was just an ordinary task, but while delivering a letter, she was forcibly dragged into a game hosted by a creature with a human body and a sheep's head, who called itself "Wei Yang."

Where did the letters this mysterious power wanted her to deliver come from? And where were they going?

What awaited her at the end of each game she entered?

One instance after another, surrounded by ghosts and monsters. Forced into the game, she had to plan each step carefully. Her only goal was to survive this endless game until she uncovered the truth behind it all.

Note:

1. Passing the game does not depend on items, but please forgive my limited writing ability.

2. This is not a horror novel.