Mei is a recent college graduate and returned to Eiden school to teach alchemy. She is very friendly and is well liked by students. Her students often refer to her by her first name and call her by friendly honorifics such as "-san" or "-chan" instead of her last name and more formal honorifics such as "-sama" or "-sensei". This makes Mei wonder if the students respect her as an adult and a teacher.
Mei is first seen on the first day when Yagami was disciplining Kazushi and his friends with his fists. She expresses her disapproval of his methods and her stern belief against physical punishment. Mei then led them to the nurse's office to patch them up. Later in class, she had the new transfer students introduce themselves to the class. When Appo- and Pierre started misbehaving. Mei started teasing the guys and told some bad jokes. The girls of the class froze as they witness Mei going at it again.
The next day, Ran led Kazushi and his friends to peek at Mei at her dorm room where she was taking a nap. Mei woke up and checks herself out in the mirror. She saw the group reflected in the mirror's image and started teasing them. Kazushi suspected that Mei knew they were there and made faces at her. Mei then laughed which confirmed Kazushi's fears. The group then ran away shortly after. Kazushi later took a walk around the school compound where he met Mei. She forgave him and the guys for peeking at her but warned them to not do it again.
After that incident, Kazushi was running low on money. Mei offered to lend him money and they share a table together. Mei is revealed to have an enormous appetite, which she attributes to her demanding job at school. Some time later at during the welcoming party for the transfer students, Mei becomes drunk and she became wild. She is able to sober up rather quickly though.
One day, Kazushi forgot the way to his class, and he wandered around the school and stumbled upon the library. Mei is revealed to be the director of the library and requests that Kazushi returns to his class. He explains that Yagami, who was teaching at that time, will punish him for being late. Kazushi explains that Yagami punches the guys because they knew that they where in the wrong.
Mei decided to taste one of Yagami's fists to better understand his explanation. When they returned to class, Kazushi explained the situation to Yagami. Yagami's fist reduced her to tears and she enforces her belief against physical punishment.
One day before the summer break, Kazushi found Mei in deep thought on a cliff overlooking the island. She confided in him and explained that she has no memory of her life before three years ago when she started working at Eiden school.
On Mei's path, Kazushi reveals his feelings for Mei and expresses his desire to spend the summer break with her. Initially, Mei was adamant against it based on their teacher-student relationship, but Kazushi convinced her otherwise. They found a picture of Mei during her student years in Eiden school. The Principal suspected their relationship and warned Kazushi against their relationship, and hints that something bad would happen.
Some time later, Mei suffered a heart attack. She was rushed to the island's clinic. Miya and the Principal reveals that the Mei is actually an homunculus created by them, and the real Mei passed away three years ago. They had no special intention for replacing Mei, and instead explained that her passing was simply an opportunity to carry out the experiment. They explained that Mei will die because she was created to give her love equally to all students, but Kazushi has upset the balance by sharing a relationship with her.
Mei overheard their conversation and asks if there is a way for her to continue living, and the Principal explains that she must purge all special feelings for Kazushi and end their relationship. Miya offered to wipe her memory clean. Kazushi and Mei decided to spend their remaining days together. Mei reasons that she is not Mei Ibuki and requests Kazushi to give her a new name. He names her Saki Haruma.
Twenty years later, Kazushi returned to teach at Eiden school. There, he met a second year student who looked exactly like Mei when she was younger and bears the name that he had given her before she passed away.
Edelweiss Eiden Fantasia
On Rin's path, Mei and the Principal discovered that Rin had been staying with Kazushi in his dorm room. When the Principal discovered the homunculus that has attached himself to Kazushi, Mei researched on the homunculus and kept Kazushi's fate secret from the rest of the class. Eventually, she was pressured to reveal Kazushi's situation.
The homunculus later revealed that there was a myth that an homunculus who had fulfilled his or her duty will reborn as a human, implying that Saki is indeed Mei incarnate.