Riko Amanai is a supporting character in the Gojo's Past Arc of Jujutsu Kaisen. She was a student at Renchoku Girls' Junior High and the designated Star Plasma Vessel for Master Tengen's merger in 2006. Riko is a young slim girl with long dark hair which is braided in the back and extends past her shoulders. She is always seen with her light hairband on the top of her head and normally wore her school uniform. The uniform was designed with striped cuffs and collars on a white long sleeved shirt with a black skirt, black stockings, and black shoes. She has also worn a black dress with white shoes. While at the beach, Riko wore a straw hat, a white hooded jacket, and a black top and bottom swim suit. Riko is an outspoken and feisty young woman who appeared to steadfastly believe in her role as the Star Plasma Vessel. She tries to keep up an aggressive facade at times, but she's really just a normal teenage girl. Riko cares deeply for her caretaker Misato Kuroi and enjoys spending time with her friends at school as well. When Kuroi was kidnapped, Riko's escorts offered to handle it themselves but she wanted to help. Riko quickly becomes flustered when it comes to people she cares about and her ability to be with them, usually crying when that is in question. Without a traditional family, Riko initially embraced her fate as the Star Plasma Vessel because she thought she was alone. However, after spending time with her escorts Satoru and Suguru along with Misato and friends at school, Riko ultimately decided she wanted to live out her life with everyone instead of merging with Master Tengen.