Who said Japanese culture is premature? In deed, Japanse doesn't have own culture at all. Sorry, Japanese for telling the truth. If you insist that Japanese should have own unique culture, it will be the spirit of the picture. I can't figure out anything more. (A US pilot beheaded by Japanese AFTER the Japanese emperor annouced surrender.)
『宋書』倭国伝 451年倭百済新羅任那秦韓慕韓六国諸軍事安東大将軍と中国からも軍事権を認められていた。 In the 28th year of Genka (451), Sei, the King of Wa(Japan), was also given the position of the envoy and military commander, governor-general of military affairs in the seven countries of Wa, Paekche, Shilla, Imna (Mimana), Kara, Shin and Kanbo and the General of Anto was restored to its original form. Also the 23 men whose names were presented to the emperor were appointed as generals and district chiefs.
478年、外交権も認められた。 Then Emperor Jun handed down an imperial decree and declared Bu the envoy and military commander, governor-general of military affairs in the six countries of Wa, Shilla, Imna (Mimana), Kara, Shin and Kanbo and the Great General of Anto, King of Wa. http://www.rekihaku.ac.jp/kenkyuu/shinpo/173.gif
『隋書』倭国伝 新羅、百済は、倭国を大国と敬仰していた。 In Shilla(south east Korea) and Paekche(south west Korea) it was thought that Wa was a great nation which possessed many rare things. Both countries respected and revered Wa (Japan) and regularly sent enjoys. http://www.rekihaku.ac.jp/kenkyuu/shinpo/174.gif