While searching through his grandfather's attic, Hikaru Shindou stumbles upon an old go board. Touching it, he is greeted by a mysterious voice, and soon after falls unconscious. When he regains his senses, he discovers that the voice is still present and belongs to Fujiwara no Sai, the spirit of an ancient go expert. A go instructor for the Japanese Emperor in the Heian Era, Sai's passion for the game transcends time and space, allowing him to continue playing his beloved game as a ghostly entity. Sai's ultimate goal is to master a divine go technique that no player has achieved so far, and he seeks to accomplish this by playing the board game through Hikaru. Despite having no interest in board games, Hikaru reluctantly agrees to play, executing moves as instructed by Sai. However, when he encounters the young go prodigy Akira Touya, a passion for the game is slowly ignited within him. Inspired by his newfound rival, Hikaru's journey into the world of go is just beginning.

Following an automobile accident that claims the life of his parents, Teppei Arima is taken in by his grandfather and introduced to the world of the rich and the elite. Compared to his humble upbringing, Isshin Arima's lavish lifestyle surprises and stuns the young teenager. In return for the gracious hospitality, Teppei is expected to continue the family business by replacing his grandfather as the head of Arima Financial Combine, and to prepare him for these responsibilities, he is enrolled into an esteemed high school. Along with his recently acquired celebrity status and affluence, Teppei is informed of an arranged marriage with the equally prosperous Sylvia van Hossen, thus, beginning the thrilling escapades of his new life!

On his first day of high school at the formerly all-girl's Ousai Private Academy, Takatoshi Tsuda is called out for his untidy uniform by the student council president Shino Amakusa. In apology for delaying Takatoshi for his first class—and stating that the group needs a male point of view to accommodate the arrival of boys at the school—Shino offers him the position of vice president of the student council. Though unwilling, Takatoshi finds himself appointed as the newest member of the student council having yet to even step foot inside the school building. Takatoshi soon realizes that the other student council members who are more than a little strange: President Shino, who is studious and serious in appearance, but actually a huge pervert, fascinated with the erotic and constantly making lewd jokes; the secretary Aria Shichijou, who may seem like a typical sheltered rich girl, but is just as risque as the president, if not more so; and finally, the treasurer Suzu Hagimura, who may act fairly normal, but has the body of an elementary school student and is extremely self-conscious of it. Surrounded by these colorful characters, the new vice president must now work through a nonstop assault of sexual humor and insanity.

3rd grade teacher Aoki Daisuke didn't expect the first class he ever taught to be one of the toughest obstacles of his life. After getting off on the wrong foot with the entire class, a moment of kind-heartedness instantly convinces one of his students, Rin Kokonoe, to make the ill-fated Aoki-sensei her lover. But what exactly are Rin's intentions for wanting to actively seduce Aoki-sensei, and will Aoki-sensei be able to help her to deal with them?