Demon King Daimaou: Volume 6 by Shoutarou Mizuki

Constant Magical Academy has a new transfer student named Keina Doronz. Not only does she have almost the same name as Akuto's friend Keena, but she also has an identical bird-shaped hairpiece -- the same one that Akuto bought for a crying girl when he was a child. Who's the real girl from his memory? To make things more confusing, this unknown girl is demanding that Akuto take her on a date!

Hilarity and magic school shenanigans ensue when Keina joins Keena, Junko, Korone, and Fujiko as they circle around our favorite hapless Demon King, Akuto Sai.