The birth of Yuriko's first daughter, Rika, should have been a joyous occasion, but it wasn't. When Yuriko looks at Rika, all she sees is an iguana. Not long after, Yuriko gives birth to another girl, Mami. When Yuriko looks at Mami, she sees a human, so she ends up loving just Mami. Rika develops a quiet, inconspicuous personality. One day Rika coincidentally hears Yuriko screaming, "That girl is an iguana from Galapagos!" When Rika looks in the mirror, her reflection is that of an iguana. Nine years pass, Rika is 17 years old; Mami 15, and they both attend the same high school...

Rika drops the form that says which college she wants to attend. Kaori picks it up by accident, and sees that Rika is applying to the same college as Noboru. Kaori gets extremely jealous, and tells everyone in class about how Rika attempted suicide in the past. On top of that, she says "The only reason you want to go to that college is because you like Noboru!" Yuriko told Rika that iguanas shouldn't fall in love because it will be troublesome to the other person, so Rika resolves to shut away the feelings she has towards Noboru deep in her heart. In shock, Rika runs from the classroom. Someone reaches out their hand toward Rika...

Yuriko is dead-set against Rika continuing on to college, but with some persuasion eventually allows it. An elated Rika informs Nobuko of the news. Nobuko is very happy for Rika, and invites her to go to Kiyosato the next day. Rika, who had never gone out with friends even once, is thrilled. However, Kaori is eavesdropping on their conversation and hears their plan. Kaori convinces Noboru to come with her to Kiyosato, and they both appear before Rika and Nobuko together...

In biology class, Rika passes out from the shock of seeing a slide of an iguana. Worried, Noboru decides to visit Rika's house to see how she's doing. However, Yuriko tells him not to get any closer to Rika, and sends him away. Of course, she doesn't mention anything to Rika about his visit. Noboru's last track meet is approaching, and Rika is thinking of going with Nobuko to cheer him on. Rika has been watching Noboru run every since they were very young. However, on the day of the track meet, Yuriko wants to take Rika shopping...

Rika's birthday is approaching. Nobuko asks Rika what her birthday wish is, and Rika replies that she wants to go to an amusement park with a person she loves. Since Yuriko has forbidden Rika to fall in love, Rika doesn't think her dream could ever possibly come true. Unexpectedly, Noboru invites her to an amusement park to thank her for helping him study for midterm exams! Rika is so happy, she's beside herself. However, Rika can't stop thinking of her mother's words, "You are an iguana!" and she turns down Noboru's invitation.

After Mami finds out she's in danger of failing a course, her mother enlists a private tutor to help her study. Since Mami is busy studying, Rika takes over Mami's part-time job at a restaurant. Since social skills aren't Rika's strong point, she struggles with the job. One day, Mami's private tutor comes to the restaurant, and Rika overhears him talking about how he's trying to sleep with Mami, and she gets extremely angry. After that, Mami finally realizes how kind Rika is, and gives Rika the ticket to the amusement park. Noboru had brought them to Rika's house on her birthday. Clutching the ticket, Rika runs towards the amusement park. Little by little, Rika's surroundings are somehow changing...

At the amusement park, Noboru tells Rika, "To be honest, I don't like the person you've become. I want you to go back to being the cheerful person you were when we were 8." Hearing this, Rika begins to want to change herself. Rika tells this to Nobuko. Nobuko wants to know the cause of Rika's depression, and asks Rika to tell her. However, Rika can't bring herself to talk about it, that she thinks she's an iguana... Mami confronts Yuriko, asking her why she's so mean to Rika、which causes Yuriko to stay in bed all day...

Yuriko tells Rika that a long time ago she had wanted to kill Rika, and herself. Shocked, Rika runs from the house. Nobuko hears of Rika's disappearance, and desperately searches the city for her. When she finds her, she takes her home to her house. The next day, Nobuko's mother tells Rika that Nobuko had a lot of problems in the past as well. Overwhelmed by Nobuko's kindness, Rika decides to tell her everything. Rika tells Nobuko, "I'm an iguana..."

Rika is convinced Nobuko's death is her fault, and shuts herself up in her room. A worried Mami tries to get Rika to come to school, but as soon as Rika sees Nobuko's empty seat, she runs out of the school. As she listlessly walks down the street, Nobuko's boyfriend calls out to her. He hands Rika a letter Nobuko had sent him earlier. In the letter, Nobuko writes, "I want to help heal Rika's heart. She has a right to be happy." Overwhelmed by Nobuko's kindness, all Rika can do is cry...

Rika has decided she will become happy, and against Yuriko's protests, moves into her own apartment. She also starts a new part time job, and appears more cheerful to Noboru. However, Yuriko is convinced she should have died together with Rika a long time ago. Finally, Noboru realizes his feelings for Rika, and asks her to come to Boston with him as he studies abroad. Unexpectedly, Yuriko tells Rika to go with him, but before she wants to go on a family trip together with everyone...

Prepared to die, Rika asks Yuriko for one last favor, but Yuriko refuses. It seems as if Yuriko would rather die than hug Rika. The day of Rika's departure is approaching, and Yuriko won't even show her face. Inside the house, Yuriko finds an old diary. In it, she reads that her husband helped an injured iguana in Galapagos long ago. It's finally the day of their departure, and Rika and Noboru head towards the airport...