Masaie (正家) stands alongside Masahiro as one of the two foremost representatives of the Ko- school, the group of swordsmiths that flourished in of Bingo Province from the late period through the period. Because this region contained many estates (shoen) belonging to major shrines and temples of the Kinai heartland, frequent exchange with Yamato fostered a pronounced Yamato temperament in workmanship. At the time, certain works display an -like manner, suggesting influence from smiths of neighboring Province. Dated examples bearing the Teiji and Sadaji era inscriptions indicate that successive generations worked under this name, with the lineage traceable to the end of the period around the Karyaku and Tokuji eras.
Masaie's forging typically shows with areas of mixed in, tending toward ; and appear frequently, while the steel takes on a somewhat dark, iron-colored tone with a -like effect. His is characteristically a tempered in , with entering well, and fine and appearing within the tempered area. A slight -like aspect along the and the presence of clearly display the Yamato-tradition traits absorbed by this school. The is rendered -cho with , turning in with a long return. Where Masahiro's works often have ordinary proportions with , Masaie is frequently seen in examples of bold construction culminating in a large .
Masaie's oeuvre encompasses forms ranging from to powerfully built of exceptional length that embody the characteristic period aesthetic. Even in blades of great dimension, his forging shows not the slightest looseness, from which his high level of skill can be inferred. His straight is executed without any breakdown, and the internal activity observable within the tempered area constitutes qualities well worth savoring. Signed works by Masaie are comparatively rare among surviving examples, and blades that preserve their hold exceptionally high documentary value for understanding both this smith's individual manner and the original form of -era swords.