|Song||Six Trillion Years and Overnight Story|
Riku (リク Riku) is a fifteen year old boy and the main character of the Six Trillion Years and Overnight Story novel.
- Riku has white hair and blue eyes. He wears a black sweater with white patterns on it and has white pants which go down to his knees. He also wears two belts that crosses his legs.
- Before meeting Ai, Riku had no name and was merely addressed as "Taboo Child" (忌み子). He was beaten on a daily basis and saw no reason for his existance. It is also demonstrated several times in the book that Riku cannot feel pain.
- Upon meeting Ai, Riku found a reason to live and slowly came to fall in love with Ai. She gave him a name and taught him how to speak. They both agree to go look for the device that grants wishes (the VOXX) together, and run away from the small village they were both confined in.
- Unlike the other novels, Riku has his wish granted at the end of the novel, as he cannot talk at the start and resists Maki's offer to grant him anything. In vain of Ai's death, he wishes for everyone in the world to disappear.
- Ai named Riku from the word 陸 (reads as riku) meaning 'land' or 'plain'. Her reason was because wherever she went, she would always be together with the land (陸).