Angela Aki - "Tegami (Haikei Jūgo no Kimi e)" (手紙 ~拝啓 十五の君へ~, "Letter: Greetings to a 15 Year Old")
Angela originally wrote this Choir song by a request of NHK, the national public broadcaster, as the compulsory song in the 75th NHK National School Music Contest in 2008, Junior High School (12–15 years old) Division. Arranged by Hiroaki Takaha, the girls' and mixed demonstration choirs were broadcast in March 2008. It was ranked at 25 on "Billboard Japan Hot 100 Songs" chart and later also used in the Anime movie Colorful (released in 2010) and the movie Have a Song on Your Lips (released 2015, you can find the snippet of the song being performed with english subtitles on youtube, the lyrics are beautiful, no wonder some students cried in the video above).