Feng Jun ultimately spent 10,000 Spirit Stones to buy three Soul-searching Talismans, as he really wanted to understand the true nature of Tempura Hiro.
He didn't expect that ordinary interrogation methods would reveal much—Ni Hong people are quite rigid, not to mention Tempura Hiro's crazy obsession with being accepted by the native Ni Hong people.
However, before interrogating Tempura Hiro, he first needed to figure out what that double-headed snake-tailed shadow was.
Even though he had the mobile phone system, which could detect all kinds of strange things, the display on the mobile described it as "an evolvable Yin Spirit, including but not limited to devouring Yin Spirits and incense fire Patronage."
After all, the mobile system is great, but without sufficient data, it's hard to make systematic inductions.
He wanted to figure this thing out first in order to strike at Tempura Hiro—knowing your every tiny secret makes it easier to keep you in check.