Riko is a young girl with long black hair that extends past her shoulders and is branded.
She wore a light colored hairband, a sailor uniform with a black and white striped cuffs and collars, a white long sleeved shirt, black skirt, black stockings, and black shoes.
Riko is also shown to have wore 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.
When Riko was young, her family was killed in an accident and was taken care of by Misato from then on.
Riko is found to be a match to merge with Tengen, which she doesn't mind. As Riko, along with Misato, are waiting at a location for Geto and Gojo, when they are suddenly attacked by soldiers of Q. Riko is rescued from the Q soldiers by the arrival of Geto and Gojo. After the Q soldiers are defeated, Riko wakes up and wonders who Geto and Gojo are. Misato tells Riko who Geto and Gojo are, which the two wonder why Riko is so spunkier. Riko explains to them how she views the merging with Tengen, and starts to yell that them with they stop listening to her. Riko suddenly notices that she is really late for school, and has them take her to school.
Riko then attends her classes when she arrive at her school, but doesn't have Geto and Gojo stay by her side. Riko is attending music class, when Gojo arrive and drags her away since intruders have invaded the school. As Riko is being brought to the magic college by Gojo, the two encounter an intruder who is capable of cloning themselves. As Gojo takes out the intruder, Riko gets a phone call and informs Gojo that Misato has been captured by the enemy. After receiving information from the kidnappers, Riko discuss with Gojo and Geto about how they will rescue Misato. The three then heads to Okinawa and manage to rescue Misato.
After the rescue, the four decide to enjoy Okinawa before heading back. When its time to leave, Riko convinces the others to stay one more day. The next day, the four leave Okinawa and arrive at the college but are suddenly attacked by an enemy. Riko is quickly brought into the college by Misato and Getou, while Gojo faces the enemy. Once the three reach the Tombs of the Star Corridor, Riko and Misato have a tearfully goodbye. Afterwards, Riko and Gotou head further into the tomb while leaving Misato behind.
Once the two reach the main chamber of the tomb, Getou give Riko direction on were Tengen is at. When Getou tell her that she can also leave, Riko explains how she was originally okay with the merge but know she just wants to be with everyone some more. Getou then says that he will take her away, but Riko is suddenly shot by the intruder. After Getou is defeated by the enemy, Riko's body is taken to the headquarter of the Star Religious Group. Later Riko's body is taken from the Star Religious Group by Gojo.