Below is a reconstructed scene of a music instrumental band of the Kofun period. The figures and instruments are based on actual haniwa ceramic funerary statues found in tombs of the era.
Source: 衣食住にみる日本人の歴史 | 旧石器時代~古墳時代―私たちの暮らしのルーツ, by 西ヶ谷 恭弘 … This is a really accessible and helpful illustrated resource on the lifestyle and living environment of the prehistoric to protohistoric peoples of Japan.
Actual kotos have been found in tomb sites too, below is a reconstruction from an artifact..
Reconstructed model of a koto instrument
Heritage of Japan 