Short answers, pulled from the story.
A butsudan is a shrine or altar commonly found in Japanese Buddhist homes, either an ornate platform or a wooden cabinet with doors. It is used for venerating the Buddha, paying respects to the recently dead, and honoring ancestors. It typically houses a statue or painting of a Buddha or bodhisattva, or a calligraphic mandala scroll.
A butsudan typically holds a honzon (a statue, painting, or scroll of the Buddha or a Buddhist deity), along with butsugu accessories including candlesticks, incense burners, bells, and offering platforms. Nearby items often include tea, water, fruit, rice, flowers, candles, hanging lamps, and evergreens. A rin bell is frequently placed alongside for use during prayers.
Ihai are memorial tablets engraved with the names of deceased family members, placed within or near the butsudan. Most Japanese Buddhist schools use ihai or kakosho death registers, and some place urns of cremated remains there as well. Jodo Shinshu is a notable exception, generally omitting ihai and using photographs of the deceased instead.
In many rural Japanese villages, more than 90 percent of households possess a butsudan. In urban and suburban areas, ownership can fall below 60 percent. The rate of ownership varies significantly between rural and urban communities.
In some Buddhist schools, replacing or repairing a butsudan is followed by a re-enshrinement ceremony. This ritual treats the transition of the sacred object as a significant spiritual act rather than a routine household matter.
The arrangement varies by school primarily in the central honzon, which reflects the particular Buddhist tradition the family follows; it may be a statue, painting, or embroidered scroll containing mantric or sutric texts. The inclusion of ihai tablets, kakosho death registers, or urns also differs by sect, with Jodo Shinshu typically substituting photographs for tablets.