鞍上人なく鞍下馬なし
あんじょうひとなくあんかうまなし
riding a horse so skillfully that it appears as if man and horse have become one
鞍上 is read as あんじょう (anjou) and means on top of a saddle.
あんじょう
anjou
あんじょうひとなくあんかうまなし
riding a horse so skillfully that it appears as if man and horse have become one