Hereditary Jutsu? To steal from the live action a bit...(just offering input, mind)
Highly stressful situations cause her bloodline limit to invoke, awakening her protector 'personality', who, like Usagi, is competent in her skills. But... unlike Usagi... this personality is utterly ruthless and shows no mercy to her enemies. Which is something that can most definitely be said of Live Action Serenity-mode. Cold, and utterly unforgiving. And several grades more powerful, too, but I don't know how that would translate, unless you stole the main plot behind Naruto and had something sealed in Usagi....
"This hand of mine glows with an awesome power. Its burning grip tells me to defeat you....
Shining FINGER!" -Domon Kashuu, Mobile Fighter G Gundam
Highly stressful situations cause her bloodline limit to invoke, awakening her protector 'personality', who, like Usagi, is competent in her skills. But... unlike Usagi... this personality is utterly ruthless and shows no mercy to her enemies. Which is something that can most definitely be said of Live Action Serenity-mode. Cold, and utterly unforgiving. And several grades more powerful, too, but I don't know how that would translate, unless you stole the main plot behind Naruto and had something sealed in Usagi....
"This hand of mine glows with an awesome power. Its burning grip tells me to defeat you....
Shining FINGER!" -Domon Kashuu, Mobile Fighter G Gundam