The Kamidana exists to house the Ofuda (yearly symbol of Okami).
Having the Kamidana/Oyashiro in your home, office or dojo generates a truly wonderful fresh feeling.
Everyone can go outside in the morning, bow and clap and give thanks to Taiyo (Sun/solar progenitor) Shinto teaches us that we receive our lives from Amaterasu Omikami (Primal Amatsu Kami) and it Sarutahiko-no-Okami who teches us how to live (Primal Kunitsu Kami) When we can sincerely thank the Sun for giving/sustaining our lives we are experiencing Shinto thinking/feeling.
Amaterasu-Omikami was enshrined at the Grand Shrine of Ise in Mie prefecture.
She was given sacred treasures by her father "Izanagi-no-Mikoto".
These treasures where to be enshrined as Kami.
The present Kamidana has a deep relationship to the Grand Shrine of Ise.
The Grand Shrine of Ise or "Jingu" is in Ise city in Mie.
Jingu is composed of a large number of small shrines, centered around "Kotaijingu" and "Toyouke-Daijingu"...it is the largest and most revered of all Shinto shrines in Japan.
Kotaijingu (Naiku) enshrines Amaterasu-Omikami, head of all heavenly (amatsu) kami and deity of the sun.
In the divine age (Kamiyo) when the heavenly grandson Ninigi-no-Mikoto descended from the Great Plain of Heaven he brought with him the great gift of rice agriculture, the gift of Amaterasu-Omikami. Toyouke-Daijingu (Geku) enshrines Toyouke-no-Okami.
The deity of food as the source of life and patron Kami of those occupations responsible for providing food, clothing and dwellings.
The purpose of the "O-Ise-mairi"or pilgrimage to Ise is to express gratitude for these blessings and to approach the shrine of the "solar progenitor" or parent to our solar system upon whom we depend for our lives.
In the Edo period "Ise-Kou" or fraternal groups formed in every part of Japan.
When a pilgrimage was made to Jingu the amulet or "Oharai-taima" was taken home.
These Oharai-taima were also distributed throughout Japan by the Ise-Kou or "Onshi "system.
The "Daijingu-dana" or special house shrine was set up to enshrine the amulets of the Grand Shrine of Ise.
This practise was the origin of todays House shrine or "Kamidana".