The Yā'mon system (also known as the Hadur System) is a planetary system in the Xi'an Empire that consists of an F-type main sequence star, three terrestrial planets, a dwarf planet, and an asteroid belt. Discovered in III.837 (SEY 2529) by navjumper Āi se Cho'an, it was designated as a supply system for the Xi'an military and placed under its protection.

In III.839 (SEY 2531), it was re-discovered by Human explorer Teesa Morrison when she traversed the Baker-Yā'mon jump point and encountered a Xi'an military escort team. This incident led the United Planets of Earth (UPE) High Naval Commander Jianna Perry to propose that Xi'an systems connected to the UPE be placed under control of the Navy in case of an attack. It became the first system to form the Perry Line, and Humans renamed it Hadur after an ancient Human war deity. Under the terms of the 2789 Akari-Kr.ē Treaty, it was ceded to the Xi'an Empire and reverted to its original name Yā'mon.