"Hi Hello" was written by
Young K and composed by Young K, Wonpil, Sungjin, Jae, Lee Woo Min and Homg Ji-sang. The song is composed in the key
D Major and has 78 beats per minute and a running time of 3 minutes and 52 seconds.{{Cite web|last=|first=|date=|title=Key & BPM for Hi Hello by Day6 Tunebat|url= https://tunebat.com/Info/Hi-Hello-DAY6/0zDnaAWKRpibCTuSNHT8yL "Hi Hello" is a song decorated with lyrics of the content of love. With a more comfortable and romantic color than the existing title songs, the three-dimensional vocals that focus on the layer of the chorus stimulate the sensibility of the listener. {{Cite web|script-title=ko:DAY6, today (6th) new song release... I believe it even in July ==Promotion==