When Taiho Ritsuryo Code and Yoro Ritsuryo Code were established, 2000 houses of Tomokuyu may have been allotted for only Chugu and later 2000 houses may have been added for Togu.
大宝律令、養老律令制定時には中宮のみ2000戸の湯沐邑が置かれ、後になって東宮2000戸が追加されたらしい。