Rampardos said: wait, what was Kaguya trying to write in her blood.
Considering the "E" I think she was going to write down Eirin's name, like in those murder mystery games where the almost dieing people would write down the person who killed 'im in blood.
As far I understand, because Kaguya was demanding candy, and either Eirin did not liked it, or wanted some and was not going to risk that one to be the last Candy