Short answers, pulled from the story.
Buddhism arrived in Japan from China in the sixth century during the Asuka period. Prince Shōtoku, a regent born on the 2nd of May 574, championed this new faith against fierce opposition from Mononobe no Okoshi.
Honji suijaku theory emerged in the ninth century as a doctrine claiming Japanese kami were emanations of buddhas or bodhisattvas. This system allowed kami to become divine twins sharing wisdom and power with their Buddhist counterparts while retaining equal dignity.
Shrine-temple complexes formed during the Nara period by placing shrines inside temple grounds such as Hachiman shrines within Todai-ji in Nara. These sites contained both shrines and temples within a single compound where monks recited sutras while worshippers offered prayers under the same roof.
Government laws enacted in 1868 mandated the forced separation of Shinto and Buddhism through the Shinbutsu bunri order which required temples and shrines to be legally distinct entities. During the Meiji period, shrines containing temples known as jingu-ji were destroyed while temples with shrines called chinjusha were generally tolerated instead.
Contemporary Japanese religious life maintains a symbiotic relationship between the two faiths despite formal separation occurring over a century ago. Funeral rites remain entrusted to Buddhist priests while weddings usually stay with Shinto practitioners even though most temples still contain small shrines on their property.