Today, I would like to show you the Renketsushiki style, with the main keep connected to the tower through a roofed passage, called in Japanese watari yagura. In this photo, taken at the Matsumoto castle, you can see that the tower from the the right side (Inui Kotenshu) is connected with the main keep by the watari yagura.
EXIF info:
Nikon D90
Lens: 8-16mm F/4.5-5.6G
Focal Length: 8mm
Aperture: F/7.1
Shutter Speed: 1/160s
ISO Sensitivity: ISO 200