Yayoi is one of the older students in Shipon's class. Yayoi had been in Stellvia's training program 2 years before, but left after a flight training accident. She is saved by Ayaka Machida, but it turned out the "accident" was also intentionally caused by Ayaka in the first place.

Recognizing the signs of another "accident" when Ayaka took Shipon out to train alone, she warns Kouta of what might be about to happen. Kouta is able to prevent another tragedy.

Despite the attacks on herself and Shipon, Yayoi defends Ayaka when it looked like she might face expulsion from Stellvia. (wikipedia)