Mai Yamada is the older (or I should say a older sister) of Tadashi Yamada. Much like her other siblings, she had been raised Catholic by her parents and for a long time she had the same beliefs. But it wasn't until she was invited to a church group by a friend that she had discovered what God and Jesus were really all about. However, she hadn't actually believed in it much until a couple of weeks when she was in youth and it started to make sense to her. After two weeks of going to the church on Sunday's, Wednesdays, and once on a Friday, she had given her heart and soul to Jesus and became a Christian like her older sister Megami. However, when she found out that her little brother had a drug problem while he was in middle school, she was discouraged and was upset at God for letting her brother go so far with the drugs that he was hospitalized. Although when she read the Bible that she shared with her sister, she had understood more than she did before and she was able to bring her brother to Christ.

When she was a first year in Class 1A in UA high school, she met a group of people known as Neijiri, Mirio Togata, and last but certainly not least, Tamaki Amajiki. Mai had quickly started to develop a crush on Tamaki in their days at school together, especially since Mirio and Neijiri had her hang out with the three of them. While Mai wasn't in the Big Three, it didn't stop them from hanging out and becoming friends.

It wasn't until their last year of High School that Mai and Tamaki confessed their feelings for each other when she had asked him to talk with her alone. It was like any other night. Except it wasn't. Because it was the time that she had confessed to the indigo haired elf, that she loved him.