Ryuji Kisaragi's cousin and the founder of the Seven Tails company.
Nanao Eriko or Eriko comes from America and stays at Ryuji's house while she's in Japan. She wields a Lost Treasure that can releases red butterfly.
She is a beautiful and tall woman with curly brown hair and brown eyes. She likes to drink sake.
She first appears in Ryuji's classroom, taking Ryuji with her to do the society's thing. She takes him to a place near the river, and then they see an army of people taking a baggage. Nanao suspect it as a S class Lost Treasure.They try to take that baggage and the army chases them, and they accidentally unlock the baggage. Suddenly, a blonde girl with blue eyes comes from the baggage, makes them shocked. Eriko understands that the girl is not Lost Treasure, but a dragon. The girl then releases fire to the enemy.
Eriko and Ryuji takes the girl to Ryuji's room. When the girl wakes up, she starts to hug Ryuji and shouting his name. She only wants to be touched by him, forbids anyone to touch her including Eriko. From that day, they takes care for that girl (Rose).