The Timeline for the Tantaherbit TL
About 380 AD: A Champa trade fleet was blown off course and crash landed on the southern coast of OTL Kyushu. The traders return to Champa and tell King Bhadravarman of this newly discovered island. The King decides to mount a trade expedition to the island.
381-384 AD: The trade expedition reaches Kyushu and sets up a trade post in OTL Kagoshima Bay. Word is sent back to Champa of the expeditions success so far.
385-400 AD: After many years. the trade post becomes and full-fledged port and many more trading posts are set up along the coast. Hinduism (of the Shaivism sect) begins to slowly spread among the natives with whom the Cham are trading, taking on characteristics of the local religion as well as Shaivism. Indian/Cham culture also begins to slowly spread among the natives.
401-420 AD: A powerful clan rises, taking over northern Kyushu and southern Honshu. They start trading with the Cham traders and Hinduism starts to spread further among the people of the clan. Eventually the leader of the clan adopts the religion and becomes interested in Indian/Cham culture.
421-435 AD: The clan continues to expand further into Kyushu and Honshu, and now borders the Cham trading port. Hinduism and the local religion continue to mix as Hindu ideas spread among the people. The leader of the clan and the upper class continue to gain interest in Indian/Cham culture.