Ever since his first encounter with the "Giant Owl" and discovered the unique scent of "mutants", Xiang Kun has been extremely sensitive to the smell of "mutants". This scent is more distinctive and lingers longer than that of normal creatures, making it easy for Xiang Kun to pick it out from other smells.
Upon entering Zi Huan Mountain, Xiang Kun's senses, including hearing, smell, and vision, were all fully operational, gathering information from the surrounding environment on a large scale.
So even though the scent of the "mutant" was very weak now, Xiang Kun detected it immediately.
Although the main purpose of night exploration in Zi Huan Mountain was to find traces left by the "mutated parasite" and to gather information, he did not really expect to find the "mutated parasite" within the mountain, nor to find its nest via its scent.
