Originally Posted by
food
It's best to stick with historical facts.
You can make an NP from the "slaying Onda no Hachiro Moroshige" part of the story.
Onda no Hachiro Moroshige
Rank A
A technique named after the grip that decapitated Onda no Hachiro Moroshige. Damage inflicted is based on Tomoe's STR, and if Tomoe's STR exceeds that of her targets, the target is immediately slain.
After the use of this technique, the contract between Tomoe and her Master immediately dissolves, and Tomoe loses all of her weapons and armour for the remainder of the Holy Grail War.
(This was done on a horse, so it works with your Rider class.)