After all, the rule concerning souls is one of the foundational rules that form the bedrock of the Multiverse. Generally speaking, only a few gods who govern domains like Life and Death might have some connection to it.
Other gods from different domains may also wish to dabble in such abilities, but the vast majority lack the talent or opportunity.
At most, they might touch upon it at the application level, as it itself is considered an extremely profound fundamental rule.
However, someone like Kana, who is not only extraordinarily skilled in Alchemy but has also dabbled slightly in the essence of the soul, is very rare. Furthermore, the fact that he also excels in Alchemy makes him even rarer.
This is also the deeper reason why that friend, Numinel, was so eager to build a deep friendship with Kana.
To be fair, Kana's progress in the construction technology of soul creation isn't remarkably significant.
