Kamaitachi opening

In shogi, the Kamaitachi opening or Eishun opening is an uncommon flexible opening.
It was invented by amateur shogi player Eishun Suzuki. The opening can be played against Ranging Rook or Static Rook.
Kamaitachi was named after kamaitachi, which is the weasel-like mythological creature associated with whirlwinds that cut humans with sickle-like painless, bloodless wounds without their knowledge.
The Kamaitachi opening is characterized by the basic formation P-56 and S-57. Typically, the first move when playing Sente is P-76, while it's S-62 when playing Gote. As Suzuki was training in a Zen temple he asked about a book that he should read to understand Zen, and he was given a book with the title "Only This Book." At the time, he started thinking of how in Shogi talk of "Only This Opening," was not possible and hence started working on the Kamaitachi opening.

Kamaitachi vs Static Rook

The point here is not to push the rook pawn. Rather, fortify with the left gold moving to 78, left silver to 88, and right gold to 58, and then move K-69 and B-77. When bishops are exchanged, capture with the knight, and then move the king to K-89, push the pawn to P-66, and move the right gold to G58-67. This will resemble a Millennium castle, although the position of the right silver will be different.

Kamaitachi vs Ranging Rook

From its closeness to the building of a Boat castle go for a Center Vanguard Pawn. Move the right silver to S-56, and then advance it to S-65, while moving the left silver to S-66. Push the bishop to 77, and encastle with the right gold to G-68. Since it is such an elongated formation, it will interfere with the formation of the rival's castle. It is more effective against Bear-in-the-hole castles than against Mino castles.