Boarding School Juliet Vol. 12 (manga)

After a river rescue gone awry, Inuzuka loses his memories--on the day of his and Persia's one-year anniversary! The amnesiac Inuzuka is practically a different person, who proceeds to throw Dahlia Academy into confusion with a myriad of misunderstandings, like mistaking Hasuki for his girlfriend. To get his memories back, archenemies Persia and Hasuki will have to do the unthinkable--team up!