This can be a Gogatsu Ningyo (dolls representing famous samurai or characters from folk stories), a miniature samurai helmet or a miniature armor set equipped with katana, bow and arrows and nobori banners with family crests, as you can see in this photo taken inside an old samurai house in Kurashiki.
Like many other Japanese traditional customs, the armor and the dolls are not just pure decoration, they are also symbols. By exhibiting these objects, the parents are wishing for their boys to grow up strong, healthy and lucky: the helmet and the armor are to protect them from any illness or injury...
EXIF info:
Nikon D90
Lens: 8-16mm F/4.5-5.6G
Focal Length: 16mm
Aperture: F/5.6
Shutter Speed: 1/60s
ISO Sensitivity: ISO 200