Someone determined the poison for us. It's Aconitum, also called 'wolf's bane' according to he who offered his assistance.

[It's written in a hurry. Mitsuhide is deeply frightened, and needs to get this sorted as soon as possible.]

I have to go and search the stores on Isla Empieza for an antidote as a matter or urgency. Please keep an eye on Lord Motochika while I am gone, Master Gakupo. With luck it will not take me too long to find what is needed.