Mondo Douan is Kamen Rider Quiz, a Rider from 2040 that appears in Kamen Rider Zi-O.
Mondo is the son of Tamotsu Douan, a scientist who became obsessed with his work and left his son and wife. When his mother fell ill, Mondo was brought to the year 2019 by White Woz to obtain his power for Geiz and began to search for his father and discover if he ever loved his family. However, his arrival allows Time Jacker Ora to turn Tamotsu into Another Quiz, though for an unexplained reason this does not erase Mondo's powers or memories as Kamen Rider Quiz, possibly because it was created in a different year than when Kamen Rider Quiz was active. While confronting his father he comes to blows with Zi-O and Geiz and fights them off so he can face Another Quiz himself, only for Ora interfere and give Another Quiz an opportunity to escape.
Mondo later goes to 9 5 DO to have Junichiro Tokiwa fix his watch and informs Sougo and co. why he is in 2019. He easily wins that evening's trivia game in a landslide. After White Woz defeated Tamotsu the next day, Mondo attempted to confront him only for Woz to tell Geiz to take Mondo's powers.
Mondo fights Geiz, but Sougo has Woz teleport him away. He finds that Junichiro was unable to fix his father's watch, but tells him it's okay. Mondo later faces Another Quiz again by himself. With assistance from Geiz, Mondo defeats Another Quiz. Revealing himself to Tamotsu as his son, Mondo asks his father if there was anyone that he ever truly loved. Tamotsu answers by telling him he did love one thing, Mondo's mother. Having received his answer, Mondo prepares to head back to his time, but Ora turns Tamotsu back into Another Quiz again. Before Mondo can transform again, White Woz steals his powers into a Blank Miridewatch directly and uses them to finally defeat Another Quiz. Seeing that his watch has started ticking again, Mondo has White Woz return him to the future.
Kamen Rider X
Kamen Rider Amazon
Kamen Rider Super-1
Kamen Rider ZX
Kamen Rider Black/RX
Kamen Rider Kuuga