Board Thread:Episode Discussions/@comment-25319479-20170531105724/@comment-734582-20170602055955

Ravianii wrote: yeah but it got explicitly stated for sharingan, but we've seen all the hyuga activate it and no word otherwise and CHILDREN have it, no emotional trauma needed...so what gives it? Unlike the sharigan, the Byakugan is a physical eye. It manifests or it doesn't. Learning to activate the eye can be done in multiple ways, including through combat training.

It seems that while pureblooded Hyuga have a "pure byakugan" (White/lavender normal eyes), i guess Himawari's can be considered an impure byakugan. Perhaps Impure ones are more difficult to activate.

Anyway, it's still a KKG and we've seen repeatedly that KKG are not necessarily guaranteed to pass on.