From Condensation:
Toujou Souko attends a Catholic high school for girls and spends most of her days ditching class and trying to hook up with guys. She's in a hurry to fall in love and often gets into trouble. Ueda-sensei is Souko's homeroom teacher and all the girls idolize him on campus. He thinks Souko's a good kid and is looking out for her best interests... Yet he never meant to encourage her to try and seduce him...
What begins as a passionate affair becomes a true and undying love... Ai Girl is an angsty love story loaded with melodrama. It should be noted that this series has adult themes and high smut content.