Sakuya knows that the SDM will end up burning at some point or another in this comic.

Well Sakuya is a genius putting that glass window knowing that her Mistress is a vampire,truly genius

Kanzaku said:

Well Sakuya is a genius putting that glass window knowing that her Mistress is a vampire,truly genius

This is the same Sakuya that put the divine blood of the Hakurei into a replica of the Holy Grail for her Master (devil) to drink