[1] He grew up listening to a wide variety of music, as his father ran a business that acted as a cafe during the daytime and as a bar at night.

[3] He was inspired to write lyrics by the large number of second hand books his father bought, such as those of Kenji Miyazawa, Osamu Dazai, Chūya Nakahara and Yoshiro Ishihara, as well as haiku poets Santōka Taneda and Shūji Terayama.

[6] After six years together, Dutchman broke up due to creative differences, when Yamaguchi tried adding electronic elements into their music, especially on the song "Mikazuki Sunset".

[5] Sakanaction made their major debut in 2007 when three additional members of the band joined and together they produced the album Go to the Future under the Victor Entertainment sublabel BabeStar Label.

[12] Since "Aruku Around", the band has seen greater commercial success, with their albums Documentaly (2011) and Sakanaction (2013) both certified gold by the Recording Industry Association of Japan.

[17] In 2010, Yamaguchi was a featured vocalist on Base Ball Bear's album Cypress Girls, on the song "Kimino-Me".

He collaborated with Base Ball Bear vocalist Yūsuke Koide in 2011 to write the song "Kodona no Kaidan" for idol singer Shiho Nanba, who released the track as a single.