"Happy Birthday to You" is a folk song traditionally sung to celebrate the anniversary of a person's birth. The melody comes from the song
"Good Morning to All"first appearing with the new lyrics in 1912

It was sung a.o. to Momoka in the seventh "Sakazaki Kounosuke
no Momoiro Folk Mura" episode in 2015

Mus: Patty & Mildred J. Hill, Lyr: Preston Ware Orem & Mrs. R.R. Forman

TV version:

Lyrics

Happy Birthday to You
Happy Birthday to You

Happy Birthday Dear [.....]
Happy Birthday to You