Kamidana has three types. The one that is commonly seen is a small-sized miyagata (literally, "a shrine shape"), inside which the shinsatsu (ofuda) (the talisman) of the Ise-jingu Shrine, ujigami (literally, "the guardian god of the family or the community"), or the god in whom one believes, is placed. This is called a fudamiya (literally, "a shrine for a talisman), and it is referred to as a kamidana in a narrow sense. A family like that of a Shinto priest, which conducts a funeral according to Shinto rites, has a kamidana to enshrine the souls of the ancestors, which is equivalent to a butsudan (a Buddhist altar) in Buddhism, and this is called a mitamaya (literally, "the abode of the souls of the dead"). There is also a kamidana that enshrines a 'goshintai' (an object of worship that is believed to contain the spirit of a deity), which carries a strong sense of the abode of a deity, instead of a shinsatsu. There is a point of view that in such a case it is more natural to consider it a spin-off of the shrine that has given it the 'goshintai' than to regard it as a kamidana. In what follows, explanations are offered concerning a fudamiya (a narrowly defined kamidana).
A kamidana is set up facing south or east near the ceiling of the top floor (or a part of the ceiling above which the upper story does not have a floor) of a room that is as bright and clean as possible. When it is difficult to be installed on the top floor, it is put in below a piece of paper on which the letter of 'ten' (the sky) or 'kumo' (a cloud) is written. Although most miyagata to which shinsatsu are offered have one or three spots into which they are put, some large-sized kamidana have more than five or seven. In the case that there are three spaces, the shinsatsu of the Ise-jingu Shrine (a taima) is dedicated in the center, that of the ujigami in the right facing the kamidana, and that of the other revered shrine in the left. In the case that there is one place, three shinsatsu are put together in the following order from the front: the shinsatsu of the Ise-jingu Shrine, that of the ujigami, and that of the revered shrine.
Shingu (ritual articles)
A shinkyo (literally, "a sacred mirror"), sakaki (sacred evergreens), and tomyo (votive lights) are arranged in front of the kamidana, and shimenawa (sacred rice straw ropes) are hung in front of them. In addition, masakaki (sacred evergreens decorated with a silk flag that has five colors, i.e., green, yellow, red, white, and blue) (a miniature), decorative tokkuri (sake bottles) (mostly of the kutani ware style) with male and female butterfly-shaped mikiguchi (plaques put on the mouths of the bottles), and gohei (wooden wands decorated with shide (zigzag paper streamers)) (kinpei (gold gohei)) are sometimes included in a set of ritual articles. It is also not uncommon to see different good luck charms (a hamaya (a decorative arrow supposed to ward off evil), a rake, and others) displayed in each household.
Shinsen (osonae (offerings))
Rinsed rice (or boiled rice), salt, water, and sake are basic to shinsen, but fruit and vegetables, raw fish, dried fish, confectioneries, and others are also offered. It is considered good to change rice, salt, and water every morning and sake and sakaki twice a month (usually the first and the fifteenth of the month, or else a day remembered in connection with the saijin (the god to whom the shrine is dedicated) whose name is written on the enshrined shinsatsu). In addition, the acceptance letter, the noshigami (wrapping paper for a present) enclosing the celebration gift, and so forth are sometimes dedicated.
The arrangement of shinsen is as follows when there are rice, salt, and water: water, rice, and salt from the left facing the kamidana or water and salt from the left in the first row and rice in the second. When there are rice, salt, water, and sake, they are placed in the following order from the left facing the kamidana: water, sake, rice, and salt, or water and salt in the first row and sake and rice in the second, or water and salt in the first, sake in the second, and rice in the third.
The food offered to the god is later eaten as 'osagari' (offerings withdrawn).
It is desirable for the entire family together to thank the god for his constant divine protection and pray for future safety and happiness following the presentation of shinsen, but when this is not possible each member may offer a prayer before going out. The style of worship at the kamidana that is recommended by the Association of Shinto Shrine is the same as the one used to worship at the shrine, which is 'nirei nihakushu ichirei' (two bows, two claps, and one bow), but there are various styles of worship like 'nirei yonhakushu ichirei' (two bows, four claps, and one bow).
Kamidana in budo-dojos (martial arts training halls)
A kamidana is placed in many martial arts dojos, but in the Edo Period it was not a kamidana but a kamidoko (an alcove in which a kakejiku (a hanging scroll) is hung) that was installed. A kakejiku bearing the names of the two pillar gods, 'the Kashima-jingu Shrine' (Takemikazuchi) and 'the Katori-jingu Shrine' (Futsunushi no kami) who are referred to as 'the god of swords, the god of war' in the Japanese mythology, such as "the Nihon Shoki" (The Chronicles of Japan) and "the Kojiki" (The Records of Ancient Matters), was placed. In the last days of the Tokugawa shogunate, as the idea of Sonno Joi (slogan advocating reverence for the Emperor and the expulsion of foreigners) gained momentum, the one containing the names of the three pillar gods with the addition of 'the Ise-jingu Shrine' (Amaterasu Omikami (the sun goddess)) in the center was used.
After gekiken (renamed kendo after kenjutsu) and jujutsu (later changed to judo) were introduced to extracurricular lessons in junior high school under the old education system in 1911, what was installed in martial arts dojos became a kamidana. The Japanese national flag was hoisted below it, and keiko (practice) was performed in the form of shinzen-keiko (practice according to Shinto rites) which included worshipping to enter the dojo. When budo (martial arts) was resumed after being forbidden in school education by the General Headquarters following the World War II, the kamidana was removed from many public school dojos based on the separation of religion and state. While it remains in some public and many private schools, it is not set up in public judo or kendo training halls when they are newly built.
Altars set up for the sakazuki-goto events (sharing of sake from a single cup as a pledge of the boss-henchman relationship) of the yakuza (the Japanese mafia) (bakuto (gamblers), tekiya (crooked peddlers))
The altars established for the sakazuki-goto events of the organized groups of gangsters look similar in form to the kamidoko placed in budo-dojos, but they do not fall under the kamidana category as they are not permanent. This practice is more like the custom of hanging a kakejiku, on which the names of the gods are written, in the tokonoma (alcove in a traditional Japanese room where art or flowers are displayed) of a zashiki (a tatami-matted, Japanese-style room for receiving guests) at wedding and other events.
It is often the case that bakuto put a kakejiku that has a width of three pieces of standard-width cloths containing the names of the two pillar gods, 'the Hachiman-shin or Yawata no kami' (the god of war) and 'the Kasuga-taisha Shrine', or alternatively 'the Emperor Kanmu' and 'the Emperor', on either side of 'the Amaterasu Omikami', and tekiya the one bearing the names of 'the Amaterasu Omikami' and 'the Emperor' on either side of 'the Shinno' (the god of agriculture and medicine).