Shingyoku's male form is often considered the 'negative' and Shingyoku's female form the 'positive'. This fan theory is closely linked to a different one which states that Shingyoku doesn't change forms but splits into two different people.
A small infamous joke is that Shingyoku is in fact a hermaphrodite, looking at how he has a female and a male form.
Some works portray Shingyoku as Reimu's parents, or foster parents; at least one work has Shingyoku look after Reimu when Konngara killed her parents.
The male half is referred to as "Shin" and the female half is referred to as "Gyoku."