If anyone can identify these, let me know.
The top one is an instrumental track. The second one below that sounds like the marvelous Chikuzen Sato（佐藤竹善）from Sing Like Talking. I have no idea about No. 3 or No. 4 while the fifth, a male solo, has that Hiroshi Sato（佐藤博）vibe. Finally, No. 6 is another instrumental track.
January 23 2020: A partially happy update on the above tracks. Misha was able to track down a couple of the mystery songs.
For the second one from the top that I had initially assumed was Chikuzen Sato, it is actually Yudai Suzuki's（鈴木雄大）"Just Your Life" (Heisei version) from his March 1989 album "Kimi no Heart ga Kikoeru"（君のハートが聞こえる）. Dang, it is smooth!
The other track is No. 4 from the top, and it belongs to Light House's "Minami Taiheiyo"（南太平洋）from their 1985 album "Box Seat".