"Diary 2016-2019" is a first music archive compilation of Akira Kosemura's music composed between 2016 and 2019, selected by the artist himself. All the music included in the album are the first time to be released on CD, and not been released on either CDs or records previously. As this album titled as "Diary", all the tracks are listed in time order, which includes the original sound track for "Konatsu and Hiyori" (Kansai TV Production), a music composed for the ending scene of French movie "Mais vous êtes fous (Losing It)", a short composition series 'In Moonlight' produced during the score production for "Chūgakusei Nikki" (TBS TV Drama), 'You' which was used as a theme song for an American TV Drama "Love Is __", a rework version of 'Someday' featuring Devendra Banhart, and 2 unreleased tracks 'Red Diary' and 'Late Night Tales'. With total of 17 songs included in the album. This album can be an introductory piece for piano music lovers, but also can be recommended to soundtrack fans. It is a music diary written with a piano, colored with his sensitive emotions.