It was called "the sweetest manju in Nagasaki" because in order to keep good quality in the summer, the chestnuts were boiled in syrup until all the syrup was dissolved.
昔は夏場に日持ちさせるために栗を煮るのにつかう汁を煮詰めていたため、「長崎一甘い饅頭」と呼ばれていた。