The envelopes are tied with Mizuhiki cord, made of twisted washi (Japanese paper) stiffened with glue. The cord is sometimes painted, but the most stylish ones are covered by brightly colored silk. Of course, like any other Japanese custom, the node has a specific meaning, it connects the hearths of the people exchanging the gifts and even more than this, the shape of the node sends a supplementary message: for example, the node on the right of this photo, shaped like a crane, is also a wish for long life, because the crane signifies longevity...
EXIF info:
Nikon Df
Lens: 24-70mm F/2.8G
Focal Length: 24mm
Aperture: F/5.6
Shutter Speed: 1/80s
ISO Sensitivity: ISO 1600