Si Yoyo is a story about the life of a man is his early twenties. A man who has the limited I.Q of an eight year old child. Has a naïve outlook on life. For him, everybody is a friend and every problem is a game that he solves with a smile. He fills his days being kind to everybody. He doesn't care if it's a bad person or someone who hates him. Because for Yoyo, everything is beautiful. He gets this trait from his mother, Lastri (mid forties) an ex-elementary teacher who left her job to raise Yoyo, her only child whom she loves very much. The Javanese woman with her mature and wise personality never gives up trying to convince her husband that Yoyo is a gift from God. But that is opposite of what Priono (late forties), Yoyo’s father, thinks. This temperamental man feels that Yoyo is nothing but a curse on their life. His father rejects and often reprimands Yoyo. But Yoyo never hates his father. He still cares about him, loves him and worships him. For him, his father is a hero.
Viola, a beautiful and rich girl (early twenties) from upper middle-class society, is a typical urban teenager, who is critical and independent. She doesn't want to be told what to do by her mother or her boyfriend. This is very different from Sasmita, (early forties) her mother. A beautiful woman, Viola is authoritarian and smart and always emphasizes the importance of discipline and education. Viola becomes stressed when her teacher rejects her course work. She is desperate when she meets Yoyo after a car incident. For Viola, Yoyo is an inspiration for her course work. Yoyo agrees. But there is a big problem. One day, Lastri finds her son whom she loves very much bruised after an interview with Viola. Lastri gets very angry because her son is being exploited by Viola. She bans Yoyo from meeting Viola. Of course, Viola is confused. She has a dilemma and her thesis is almost at the dead line.
Laila, a country girl, has been Yoyo’s best friend since they were in elementary school, even though Yoyo could not finish school. He is often Laila's savior from the village scamp, Abron. Abron hates Yoyo and gives him the name 'Si Lemot' (weak brain). Laila falls in love with Yoyo.
Meanwhile, Yoyo makes friends with a group of four kids. Together they play games and enjoy their childish world. He doesn’t realize that there are two beautiful women in love with him. His philosophy in life is very simple; 'be good and forgiving'. Someday God will give him 'The Gift'. One day he will become a normal person.