Shiratori Sakuto is 28, but has the intelligence of a 6-year-old boy. He works for ‘Dream Flower Service’, a flower distribution centre which provides employment for problem youth including those who have been in juvenile corrective institutions. One day, Sakuto and a colleague, Yanagawa Ryuichi, deliver a rose bouquet to the apartment building where Mochizuki Haruka lives. Because Haruka does not know that the deliveryman is mentally challenged, she is shocked by his response and tries to call the police. Yanagawa hurriedly rushes over to explain the situation and seems to settle the matter. However, Sakuto gets drawn to a pair of glittering earrings on an accessory stand at the entrance’s display shelf and reaches over with his hand. This creates another commotion. The pure, kindhearted Sakuto can barely do a delivery, but his dream is to become a “good boy” whom his mother will like. On the other hand, at the brain physiology research centre which Haruka works for, team leader Professor Hachisuka Daigo has been studying the improvement of mental performance and succeeded in lab experiments on a white mouse called Algernon. A presentation to a pharmaceutical company also goes well because of him and the clinical trial, which is the next step, will be backed by the company president, Kawaguchi Reiji. However, researchers, who have returned from the presentation, voice worries that this is premature. Nevertheless, Haruka blindly believes in Hachisuka’s judgement. She is drawn to him both as a scientist and as a man. The team immediately proceeds to facilities which help people with disabilities. They search for subjects for the clinical trial, but have difficulty finding people who will give consent in view of the risk of side effects. In the midst of this, Algernon escapes from his cage and goes missing. They determine his location via GPS but cannot find him. At that moment, Sakuto has gone to pick up girls at Shibuya with his colleagues. Doing just as they told him to, he stands alone on the road and calls out to females. However, he gets entangled with a rough guy who punches him. A bloodied Sakuto falls over on the roadside. A white mouse approaches him … … Sakuto is transformed into a genius through surgery. But when Algernon’s new intelligence begins to fade and he dies, Sakuto realises that his genius, too, is destined to leave him.