Combs were common burial items for females buried in both Chinese and Japanese tombs since prehistoric times.
The practice of performing purification rituals and sending wine cups down the river mentioned in the Chinese texts quoted by Michael Como and excerpted below, is similar to the harae rituals performed in Asuka and Nara.
From “Weaving and binding: immigrant gods and female immortals in ancient Japan” by Michael Como
“…combs and robe left behind in Takeru’s tomb combs are a substitute focus in tombs for worship for women who are believed to have reached Land of immortals beneath the sea Mononobe’s Oto Tachibana Hime consort of Takeru who sacrificed herself in the sea for him to an angry sea and then her comb was washed up on shore later and buried in her tomb.
Similarity to the Luck of the Sea Pinyuan sheng, Henan 6th century Chinese text Hsu Chi CHieh Chi, 469-520, during the time Han Chang Ti third day of third month, Hsu Chao had three daughters born to him on the third day , but all three died by third day entire village went down to water’s edge to purify themselves and to send wine cups down the river. The origin of the banquets at the river must be here.”