Amaryllis, Ginro and Kohaku are chosen to join the inner palace. The science team will need a way to communicate with them in secret, and, eventually, a way for them with the science team.
so Kohaku-chan must have been 
the one using her blood to write.
.لذا لا بدّ أنّ كوهاكو هي التي استعملت الدم للكتابة
also muss Kohaku das mit
ihrem Blut geschrieben haben.
quindi il simbolo del sangue 
l'ha scritto la cara Kohaku.
então a Kohaku deve ter 
usado o sangue para escrever.
так что художником была Кохаку.