"An offshoot of the mainline school of Yagyu Shingan-ryu centered in Sendai in Miyagi Prefecture. Morihei UESHIBA trained in this art in Sakai near Osaka from c. 1903-1908. Ueshiba's practice began around the time he entered the army and continued after his discharge when he would periodically commute from Tanabe. The technical content of this school is unknown but certainly included jujutsu techniques and the study of various weapons. Records are unclear as to whether Ueshiba's direct teacher was Masanosuke Tsuboi or Masakatsu NAKAI. Ueshiba received a transmission scroll from this school in 1908 but the document bears no seals thus shedding doubt on its authenticity."
From Aikido Journal