For example, the most classic First Tier Profession Skills, Zhang Yanhang obtained a total of four skills at First Tier: Technique Immunity, Seeking Fortune and Avoiding Evil, Gun Master, and Fighting Master.
The latter two skills obviously came directly from his previous Gun Proficiency and Martial Arts Proficiency learned from skill books after career advancement to Heavenly Destiny Master.
Seeking Fortune and Avoiding Evil is similar. At that time, Zhang Yanhang had an Enemy Seeking Radar; he was constantly complaining that the radar was useless, and as a result, he obtained the Seeking Fortune and Avoiding Evil skill during career advancement and completely eliminated the radar.
As for Technique Immunity, it is highly possible because Zhang Yanhang ate an Earth Spirit Fruit before. He relied on that Earth Spirit Fruit to form a protective effect, or rather, Spirit Light Protection. Later, he acquired the Technique Immunity skill during career advancement.
