Chen Yu's Necromantic Space naturally had no living people; the maids serving tea, just like those in the previous meeting room, were all Ghost Maids.
The maids in the previous meeting had been lent by Yu Chen to Kyuuzai Ryousen for the purpose of maintaining secrecy. After all, information about Transcendents should be known to those who need to know, but better kept from those who don't. Even though Yu Chen wasn't afraid of trouble, he preferred to avoid it.
Furthermore, after the construction of the Necromantic Space was completed and the Spirit Gathering Tower was established, common Undead Servants like the Ghost Maids, who are composed only of souls, could be summoned in batches. Therefore, Yu Chen was not lacking manpower in this regard.
However, to the people from the Tsuchimikado Family, this had a different significance.