kareshi kanojo no jijou
A romantic comedy written and illustrated by Tsuda Masami from 1996 to 2005, it follows the life of the supposedly-perfect (but actually rather spoiled and slobby) Miyazawa Yukino, as she enters into a rivalry with fellow student Arima Souichirou (who also seems perfect but has his own secrets). Over time, as they learn more about each other and overcome their struggles, they go from rivals to lovers. Commonly abbreviated as "Kare Kano" and literally translated as "His and Her Circumstances", it was also turned into an anime by Gainax in 1998.
The following tags are aliased to this tag: his_and_her_circumstances, kare_kano, and karekano (learn more).