Yuniko Kouzuki

Niko, Scarlet Rain, 上月由仁子

Yuniko Kōzuki, currently known as the Red King and leader of the Red Legion in Prominence, was first introduced to Haruyuki as a kind-hearted girl with good manners. She greeted him politely and demonstrated her culinary skills. At the time, she was an elementary school student attending a private institution. Her duel avatar is Scarlet Rain, who has taken on the role of Red King after Red Rider.

Spoilers:

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. Her true identity is the second generation Red King who replaced the first one and became the leader of the legion "Prominence." Her Duel Avatars name