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. One day, he and a colleague, Yanagawa Ryuichi, delivers 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. Haruka works for a brain physiology research centre where Professor Hachisuka Daigo has been studying the improvement of mental performance. He has succeeded in lab experiments on a white mouse called Algernon.

Today is the payday of Dream Flower Service where Shiratori Sakuto (Yamashita Tomohisa) is working. President Takebe's (Hagiwara Masato) policy every month is to hand the salary of Yanagawa (Kubota Masataka), Hiyama (Kudo Asuka) and every employee as cash. As Sakuto receives his salary with a smile, Hiyama inquires, "What will you buy?", Sakuto answers, "I will become smart* and take my license." At that time, Yanagawa's mom, Kyoko (Tanaka Minako) visits Dream Flower Service. After Kyoko greets President Takebe, Yanagawa hands over to her the salary he has just received. As Sakuto and Hiyama has seen the exchange, Yanagawa couldn't hide his embarrassment over the situation. On the other hand, in the research on making improvements in intellectual advancement, Hachisuka (Ishimaru Kanji) and his research team who had successful results on the experiment using the mouse Algernon, now wants to step up by doing the clinical study to a human body but haven't found a test subject yet. However, one day, as Haruka (Kuriyama Chiaki) wants to help Hachisuka advance in his research, she reports about Sakuto to him. Thus visits Dream Flower Service and lowers her head to Takebe seeking his cooperation for Sakuto to be a test subject. That day too, being contacted by Rio (Tanimura Mizuki) and Mai (Omasa Aya), Sakuto, Yanagawa and Hiyama are unexpectedly on a date at the amusement park...

The leader of the research team who's making great advancements on intelligence, Hachisuka (Ishimaru Kanji) told Sakuto (Yamashita Tomohisa) "I'll give you magic." After that, the test for Sakuto's suitability started. But with not so favorable results, Hachisuka and his research team's expressions fell. However, Haruka (Kuriyama Chiaki) who recommended Sakuto as a test subject, insisted though that this is something they ought to do with enthusiasm and desire to improve, regarding Sakuto's tests. Hachisuka then instructs Haruka to observe Sakuto's human emotions such as joy, anger, grief and so on as well as his various desires. At that time, Sakuto heard from the one who's in charge of Algernon, Kokubo (Kikuchi Fuma) about Algernon's bride. Asked by Kokubo if he doesn't have a girl who he likes the most in this world, Sakuto ponders... On the other hand, Yanagawa (Kubota Masataka) and Hiyama (Kudo Asuka) hears from the President of Dream Flower Service, Takebe (Hagiwara Masato) about Sakuto receiving operation to improve his intelligence. Having issues with their mothers such as being deceived for money and such, worried about Sakuto's operation, they oppose. But this is Sakuto's wish, Takebe persuades Yanagawa. That day too, Rio (Tanimura Mizuki) who's been pleased with Sakuto, not listening to the objections of Mai (Omasa Aya), invites Sakuto with Yanagawa and Hiyama to a villa. In approaching Sakuto, what is Rio's real intention? At the bottom of this, the big secret being carried by Rio will set..

Finally, Sakuto (Yamashita Tomohisa) was able to receive the operation that will greatly improve his intelligence. Hachisuka (Ishimaru Kanji) and his research team conducts several postoperative tests to inspect his progress but compared to the mouse Algernon who received the same operation, in Sakuto's case, they were not able to verify a big change in terms of displaying a striking effect. "Did I become smart?" Sakuto inquires to which Haruka (Kuriyama Chiaki) replies "Believe, let's wait." Before long, Sakuto goes back to Dream Flower Service where Takebe (Hagiwara Masato) meets him saying I'm glad you're safe. On the other hand, when Yanagawa (Kubota Masataka) and Hiyama (Kudo Asuka) invites Rio (Tanimura Mizuki) and Mai (Omasa Aya) to celebrate Sakuto's recovery, a voice wanting for them to come support a baseball match a few days after the planned party calls out. One day, after Sakuto's regular inspection, Hachisuka takes out Sakuto and Haruka for a meal. Filling in as a substitute for the baseball match, Sakuto asks "If I become smart, can I do baseball?" Hachisuka tells him if your brain function improves, it's expected your physical function also makes progress. Haruka explains this to Sakuto as "You'll probably get better in baseball." Delighted Sakuto smiles and invites Haruka to come support him. Seeing that, Hachisuka starts telling the story of Adam and Eve who's said to have eaten the "forbidden fruit". However, Sakuto is not able to grasp the significance of this story. Why is Hachisuka telling the story of Adam and Eve? The aim is!?

After successfully hitting a homerun, the tests on Sakuto (Yamashita Tomohisa) by Hachisuka (Ishimaru Kanji) continued and the results have steadily made progress. That being said, finally the effects of the operation have appeared. Sakuto who started to recognize becoming smart, felt that the world he has seen is different from what he can see now. Even though he remembers to have special feelings towards Haruka (Kuriyama Chiaki), Sakuto personally still wonders how will he comprehend these feelings, he doesn't understand. However, at work he doesn't make mistakes, his desire for higher knowledge got stronger. Whenever he has time, Sakuto reads various genres of books like he's rummaging through. One day, Hachisuka who heard of Sakuto's dream of acquiring a driver's license, presents Sakuto a red sports car. Sakuto wants to go on a drive with Haruka once he gets his driver's license. Haruka smiles at him in consent. With that, Sakuto started to go to a training institute. Yanagawa (Kubota Masataka) and Hiyama (Kudo Asuka) who are protecting Sakuto couldn't hide anymore their surprise on Sakuto's changes lately. On the other hand, when Rio (Tanimura Mizuki) and Mai (Omasa Aya) asks Sakuto "why do you want to get a license?" Sakuto answers he promised to go on a drive with Haruka. Hearing that, Rio and company....

Sakuto (Yamashita Tomohisa) who witnessed the kiss between Haruka (Kuriyama Chiaki) and Hachisuka (Ishimaru Kanji) called Rio (Tanimura Mizuki) and spent the night together. The next day, Haruka who was called by Hachisuka in his office, matches the awkward face of Sakuto. Hachisuka wants Haruka to tell Sakuto the address of Sakuto's mother Madoka (Kusakari Tamiyo). Thinking "The operation was successful. When she sees myself now, mother will be delighted." Sakuto wants to meet Madoka so he requested Hachisuka. In that case, Haruka said why don't they go together so she can show him around but Sakuto said he's fine alone. On the other hand, hearing about Sakuto and Rio spending the night together, Yanagawa (Kubota Masataka) and Hiyama (Kudo Asuka) are surprised. Mai (Omasa Aya) who heard about Rio's sickness from her father (Nakahara Takeo), talks to Rio frankly about this. That time, Haruka visits Takebe (Hagiwara Masato) at Dream Flower Service. She came to install a studying device to be used while sleeping at Sakuto's dormitory. Hearing from Haruka that today Sakuto went to see his mother alone, Takebe's expression completely changed. What in the world is Takebe worried about? At that moment, Sakuto rings the intercom at Madoka's house...

Hachisuka (Ishimaru Kanji) presented Sakuto (Yamashita Tomohisa) at the academic assembly for his advance intelligence through the medicine "ALG". If this is administered to common people, it addresses that there will be no more things such as discrimination or war but a peaceful society. In the midst of the applause, Sakuto discovers among the audience the figure of his dead father Hisato (Ishida Issei) and becomes dumbfounded. Why was Hisato there? Before long, going back to the waiting room, with Kokubo's (Kikuchi Fuma) guidance, his younger sister Karen (Iitoyo Marie) who he haven't met for years is there. Karen who's overwhelmed in meeting again was just told bluntly and coldly by Sakuto to leave. Personally seeing that attitude, Haruka (Kuriyama Chiaki) reflexively slaps Sakuto. After that, Haruka just doesn't show up anymore at the research center, disappearing from Sakuto's sight. On the other hand, knowing that if Rio (Tanimura Mizuki) uses ALG her illness could be cured, Yanagawa (Kubota Masataka) and Hiyama (Kudo Asuka) are delighted. And with that, Mai (Omasa Aya) and everyone thought that Rio and Sakuto's meeting is destiny. That day too, Hachisuka and Sugino (Kaai Gamon) visited Kawaguchi (Nakahara Takeo) and reported about Rio's medical treatment. About that...?

Sakuto and Haruka wakes up happily next to each other. Rio's in the hospital. Kawaguchi wonders if this is retribution for him. He relates to Mai that there are lots of incurable diseases but they provide funding to the researches who has a lot of patients inflicted with that disease like cancer or cerebral infarction. He didn't expect this would happen to his daughter. That the researcher that he raised would not pull through in the end. Now he's confused. A knock on the door interrupts him.