The Richelieu family are a wealthy household. They have enterprises in the fashion and food industry. The Shiki Academy's uniforms are provided by the Richelieu family so the twins are treated generously as a result. With her charming and outgoing personality, Akiko maintains and establishes the business connections at the academy for the Richelieu family. Unlike her twin brother, she is quite popular especially with the female students.

As a child, Akiko encountered a girl who was able to turn flowers into a frozen glasslike state and when the sun hit them, they refracted a rainbow light. Little Akiko was enamored with the colorful world this girl made and it filled her delight. She was ethereal. She was genuine. Akiko vowed to marry her when she had grown older. Natsuki later recalled a similar experience and Akiko agreed that she had also met the Spring Maiden too.

Not wanting her brother to confess to the Maiden first, Akiko tried finding her by presenting a flower to every girl she met, which usually caused the other party to have an accidental crush on her. During middle school she is reunited with Haruki and Fuyuki, and discovered that while Natsuki's Spring Maiden was Haruki, the one Akiko had met was Fuyuki. Akiko tried confessing but her previous childhood ventures had her surrounded by girls constantly and it was hard to find time alone with Fuyuki. She noticed that the closer Natsuki tried to be with Haruki, Fuyuki seemed to pop up out of nowhere. Akiko then started staying alongside Haruki more often in order to see her.

After the troubling incident with Natsuki and their father, Akiko was more focused on Natsuki's well-being. She visits Natsuki to make sure he is taking his nutritional supplements and keeping up in school.

Being born with the Autumn attribute, Akiko has the ability to change colors. She helps her mother in choosing color palettes for their fashion products.

Her ability wasn't anything remarkable and she had little problems in controlling it. Usually having a special ability would be something to boast or gain prestige, but for Akiko, it was not the case.

Akiko worked on developing herself as a person instead, her ability didn't define her, which was probably one of the reasons why she was so popular in the first place.

• Akiko is half Japanese and half French.
  • Her French name is Marléne.
• Akiko is currently in the kendo club but with her great athleticism, she helps out in other sports clubs.
• A fatal flaw of Akiko is that she is terrible at cooking. She cannot cook even the simplest of dishes.
• Akiko and Natsuki are mirrored twins. Akiko's organs are normal while Natsuki's organs are reversed (situs inversus).
• Akiko, Natsuki, Haruki, and Fuyuki's names are made up of the 4 seasons kanji.
  • Aki is Autumn. Natsu is Summer. Haru is Spring. Fuyu is Winter.