Asagi Ayase (綾瀬 あさぎ, Ayase Asagi) is the oldest sister of the Ayase family. Her younger siblings consist of Ena (the youngest), and Fuuka (the middle child). Asagi has a friend called Torako who she hangs out a lot with and spent some time in Okinawa together, in the second volume. In volume two of Yostuba&!, Asagi is called the "devil spawn" by her mother and Asagi replies "No, I'm your spawn." (Ohhhhhhhhhhhh plays in the background). Asagi is sly and has a playful personality. She comes off to enjoy messing around with people and likes to "kill off their father".
Asagi is also considered to be undeniably beautiful by many characters in the series. Very early in the series, Jumbo developes a crush on Asagi and later, Yanda calls her a supermodel.