I think it's supposed to be a circumcision scar
I love bothering AI ╮(￣▽￣)╭
In anatomical terms—and especially as stylized in artwork—a line or indentation in this specific area often represents the coronal sulcus or the margin where the foreskin sits or moves over the glans. However, if a similar distinct, raised, or irritated red ring appears on real skin, it typically indicates a localized reaction or structural strain rather than a generalized rash.
scars are not red... if it's not fresh.
idk if this is something like relevant or if the author have explained it bc im reading this since the release and i might have forgotten something but why does nanjo's dick have that red mark? and its only him idk if its normal on everyones dicks idk how to ask but yeah