While I lived in Japan, I could not find an aikidō dōjō near the place I lived, so I trained in shōrinji-kenpō. One thing that stuck me was that half of the techniques, the soft ones, were very similar to aikidō techniques. At that time, I just assumed this was due to some vague influence and the fact that there are only so many possibilities. It turns out that aikidō and shōrinji-kenpō share a common ancestor: daitō-ryū.

The origins of that martial art are a bit nebulous, the main fact is that it was taught by Takeda Sokaku, who probably inherited the art from his clan. Takeda had multiple students, among whom Morihei Ueshiba, who founded aikidō, and Okuyama Ryuho, who founded Hakkō-ryū. In turn one of the students of Okuyama Ryuho was Nakano Michiomi, who founded shōrinji-kenpō and took the name Sō Dōshin.