Athena Tennousu

Athena is a daughter of the Tennousu family. She has mainly appeared in the manga. She has only been shown in the anime during a brief flashback where Hayate reflects on his first girlfriend. Her parents are presumed missing or dead, since she lived alone. She is Hayate's old girlfriend, as well as his first Mistress, whom he met 10 years ago. Since he was very young at that time, he called her "A-tan" for short. Her family owns Hakuou Academy, and she is the board chairman of the school. In the manga it's shown that she has feelings for Hayate despite being away from him for 10 years. Though when she meets him again she lies to him that he doesn't remember him anymore.

Later on she leaves Japan for Greece and as she's about to leave Hayate confesses to her and she replies with a kiss and thus, Hayate and Athena kissed for the first time in 10 years. In the 4th season she appears more frequent and becomes one of the tenants at Nagi's dormitory.