I received a photo from my daughter on the Line app. It showed my 5-year-old granddaughter holding a 30-centimeter-long sweet potato. She harvested it at an event held by her kindergarten. Its size made me want to send a voice message to her. After several minutes, I received a text message. It was a little strange but understandable. Then another text message arrived from my daughter. She said that the previous message was written by my granddaughter! I was very surprised because I knew my granddaughter could write her name in “hiragana,” but I couldn’t believe she could use a smartphone. Young people learn how to use digital devices and apps so easily. They are my teachers in the digital world. (121 words)