What is That Black Object Whose Kanji are Written?
“Ihai” (位牌, いはい) is a wooden plate with a posthumous Buddhist name (*1)（戒名, かいみょう, Kaimyo） on it to honor the deceased. It originates in the convention of Confucianism where the information of the dead person includes the rank and name. People consider that the spirit of the deceased lies in the Ihai, or that the Ihai itself is the deceased, so it has a significant meaning.
The price ranges from JPY 10,000 to 50,000 depending on the material, type, and size. An expensive one can cost more than JPY 300,000. The shape of the Ihai is independent of the sects, so people can choose the one they prefer. When you count Ihai, the unit is “柱” (はしら, Hashira, Pillar).
Kaimyo was originally given to people who followed the lifestyle of Buddhism or whose mind was trained based on Buddhist rituals. People generally get it once they pass away nowadays, but ideally, we should receive commandments while we are still alive and live a life as a Buddhist. In fact, most temples give “a posthumous Buddhist name before death” (生前戒名, せいぜんかいみょう, Seizen Kaimyo).
Kaimyo is called differently between sects. For example, it is called “Houmyo”（法名, ほうみょう, Houmyo）in Jodo Shinshu, and “Hougo” in some other sects. When we say “Ihai”, this usually addresses all the letters written on it (院号・道号・戒名・位号, いんごう・どうごう・かいみょう・いごう, Ingo, Dougo, Kaimyo, Igo); however, the official way is to indicate with two letters based on a secular name or the scripture. As it is always two letters regardless of the rank of the deceased, it means all the humankind is equal in the world of Buddhism.
Generally, people own one Buddhist altar per household (*2), and the ownership rate is about 40% (*3). As you can see in this image from “Magical Girl Raising Project”, people put the Ihai in the altar to honor the spirits when a member of the family dies.
There are usually several Ihai in an altar, such as a grandfather’s and grandmother’s. Having only one altar is the same concept as going to the same grave as a family. This expresses the Japanese way of thinking and customs, where we base our thoughts on the unit of the “family”, not “a person” in an event like this.
A family may have two altars when the parents of a couple believe in different sects, although this is a rare case.
According to an article in The Sankei Shimbun, which is one of the main newspaper publishers in Japan.
As Ihai is the deceased himself/herself, it is not rare that people run out of the house with it at the time of a fire like in this image from “Tokyo Magnitude 8.0”. If you look at how a Japanese person handles Ihai, you can understand his/her feeling towards the deceased. (Well, I should probably wipe the dust off the Ihai in the altar.)