The story follows a Roman architect named Lucius, who is having trouble coming up with ideas. One day, he discovers a hidden tunnel underneath a spa that leads him to a modern Japanese bath house. Inspired by the innovations found there, he creates his own spa, Roma Thermae, bringing in the modern ideas to his time.
A mysterious creature destroys 70% of the moon. The creature then warns that if he is not destroyed by March of next year, Earth will be next. The creature also demands that he becomes the homeroom teacher for 3rd grade E class at Kunugigaoka Junior High School. The government is powerless to say no. The creature then becomes the homeroom teacher of 3rd grade E class which consists of failed students including Nagisa Shiota. The creature is called Teacher Koro. Meanwhile, the government requests that the students try to kill Teacher Koro even though he possesses super powers. The government offers a 10 billion yen reward for whomever successfully kills him. The students are confused by the situation, but decide to kill Teacher Koro. When their class begins with Teacher Koro, the students finds themselves having a good time with their new teacher.
When eighth-grade cool guy Hiromi transfers from Tokyo to a small elementary/middle school with only six kids enrolled, wholesome and honest Soyo becomes enthralled with his sophisticated world.
Four years have passed since that emotional marriage proposal at Tsukushi Makino's high-school prom, and Tsukasa Dōmyōji announced his engagement to Tsukushi to the entire world. At an engagement dinner between their families, Dōmyōji's mother, who has been strongly against their relationship before, presents Tsukushi a tiara, which is estimated to be worth roughly 10 billion yen, as a token of their engagement. But that night, the tiara is stolen by somebody! Then, Dōmyōji and Tsukushi travel around the globe to Las Vegas, Hong Kong, and even a deserted island to get the tiara back—the legendary tiara that has been believed to "bring eternal love." In the meantime, where and what are the "F4" fellows, who have just gone separate ways, doing now?
While everyone thinks that Momo is a wild party girl, the reality is that she is shy and lonely. Can Momo confess her love to her classmate, Toji, or will her best friend Sae steal him away? It's a bittersweet drama of growing up and fitting in.
Problem student Haru Yoshida sits next to the cold and studious Shizuku Mizutani in class. Without any other friends to turn to, both of them start to get to know each other and grow closer. Haru eventually develop feelings for Shizuku and confesses his feelings to her. Will Haru and Shizuku get their happily ever after?
Hatori Matsuzaki is a female high school student. She has a crush on her childhood friend Rita Terasaka and believes he will eventually choose her as her heroine, but Rita Terasaka begins dating Miho Adachi. Meanwhile, the most popular male student, Kosuke Hiromitsu takes an interest in Hatori Matsuzaki.
Daikichi learns that his recently deceased grandfather has an illegitimate daughter with an unknown mother. The girl's name is Rin and she is just 6 years old. Everybody in Daikichi's family looks at the girl as an embarrassment and wants no part of her. Daikichi, annoyed by his family's attitude, decides to raise Rin by himself. Even though Daikichi himself has no experience raising a child and is still single.
As children, the introverted Smile was being bullied by a gang of kids until the brash Peco comes by and chases all of them them away. Peco then takes Smile under his wings and teaches him how to play the game of ping pong. From there a life long best friend relationship comes into existence between these two polar opposite kids.
Arata Kaizaki is 27-years-old and unemployed. He quit his prior job after working for the company for 3 months. Arata Kaizaki decides to take part in a research program. He takes medication that makes him look younger and he is to attend high school for a year. There, he falls in love with female high school student Chizuru Hishiro.