It is customary at this time to visit the temple to present offerings of pounded-rice cakes (mochi), sweets, fruit, and so on to the principal image of Buddha as well as the family ancestors.
A Buddha-altar isn't only a place to honor one's ancestors. Within the altar, there is an area where Mt. Sumeru (the mountain at the center of the Buddhist cosmology) is represented and in the center of that area the main image is enshrined.
Hoji (a Buddhist service) referred originally to the teachings of the Buddha, and familiarization with the heart of the Buddha. However, it later came to refer in general to a Buddhist ritual or ceremony, or a memorial service for the deceased.