Yuniko Kōzuki is the second and current Red King and also the leader of the Red Legion, Prominence.When Haruyuki first meets Yuniko, she has a personality of that of a normal girl. She was sweet and caring to Haru. She presented good manners such as greeting him and was shown to be able to cook well. Yuniko is an elementary student and attends a private school. Her duel avatar is Scarlet Rain who is the current Red King following Red Rider.
She is also known to have knowledge of the Incarnate System due to her being one of the Six Kings of Pure Color. She later demonstrates her abilities with the Incarnate System when she helps teach Haru and Taku to use it.
Her true identity is the second generation Red King who replaced the first one and became the leader of the legion “Prominence.” Her Duel Avatar’s name is “Scarlet Rain.” She is known to be an immovable fortress due to her Enhanced Armament which is a huge machine armed with large guns and missiles. Its sheer firepower means that she doesn’t have to move in her spot.
She pretended to become Haruyuki’s cousin by using social engineering in order to get close to him. She did this to ask for help to defeat the fifth generation Chrome Disaster who possessed one of her legion members.