|Kanji||岩永 琴子（いわなが ことこ）|
|Alias||Goddess of Wisdom|
|Age||15 (chapter 1), 17 (chapter 1)
Kuro Sakuragawa (Boyfriend)
|Manga Debut||Chapter 1|
|Voiced by||Akari Kito|
Kotoko is a young woman with a petite build and doll-like appearance, often mistaken as a young child instead. She has fair skin and purple eyes framed by short, curly blond hair. As a Goddess of Wisdom, she also has only one eye and one leg, with her right eye and left leg being prosthetics. Her glass eye looks identical to her functioning eye, and her prosthetic leg attaches around mid-thigh height.
Her everyday outfit consists of a white hat with a black ribbon, a white dress with dark blue accents, white socks, brown shoes, and a red cane. The top part of her dress has puffy sleeves and can be taken off independently from the rest of her dress.
After the first arc, she alternates between different dresses.
She has a very outgoing personality and always makes an effort to find the root of any problem, especially when she has the help of yokai. She is oblivious to danger and she tends to be very clingy when it comes to Kuro.
At the young age of 11, Kotoko Iwanaga was abducted by yokai for two weeks and asked to become their "God of Wisdom," a mediator between the spirit and human worlds, to which the girl quickly agreed but at the cost of her right eye and left leg. After what happened, whenever yokai wish for their problems to be solved, they make their way to Kotoko for consultation.
She was discovered with "her left leg amputated and her right eye carved out."
Kuro Sakuragawa: They are currently in a relationship with each other. Kotoko met Kuro, who was 20 years old at the time, at the hospital when she was 15 years old. She fell in love with him at first sight. They meet again after two years at the same hospital just after Saki broke up with Kuro.
Saki Yumihara: The two don't get along at first but eventually put aside their differences to solve the mystery of Steel Lady Nanase.
Rikka Sakuragawa: When they first met, Rikka told Kuro that Kotoko wasn't "a good one," only getting him to agree with her. After the awkward introduction, however, they became close and Kotoko even began visiting her at the hospital too.
- Her cat cane is custom made and although she doesn't need it, her family insists she uses it
- Her full name containts characters that each can be read as: "gan" from (ganseki) rock; "ei" from (eien) eternity; "koto" a Japanese musical instrument; and "ko" from child.