Seikuken is more of an imaginary skill. And it's about calming your mind and see every attack and know your range as well as the opponents. It's not like a visible circle around you. But imaginary. And so it does exist.
(That's why you only find links to the manga when you look up Seikuken because it's not real but in essence, what I've put up is what seikuken actually is.)