First loves are messy. While settling in as a shoujo manga editor at the famous Marukawa Publishing House, Ritsu Onodera is quite troubled. Working under the stern and superb Masamune Takano is hard enough as it is. However, Masamune is not only Ritsu's first love from middle school but he also suddenly declares that he will make Ritsu fall for him again. Unknown to them, another editor in the department, Yoshiyuki Katori, is in a relationship with the popular manga artist Chiaki Yoshino. The carefree Chiaki fails to notice, however, that his high school friend—Yuu Yanase—thinks of him as more than a friend. The stoic but caring Hatori will not surrender his love so easily. Falling in love for the first time when you are 30 is certainly troublesome. Shouta Kisa, yet another editor, is going out with 21-year-old Kou Yukina, an art student. Despite Yukina's assurances, Kisa cannot help but doubt whether someone like himself is truly worthy of his younger, "sparkling" boyfriend.

After having to deal with jealousy from his co-workers for working under his father's name, prideful literary editor Ritsu Onodera is determined to establish himself in the industry. To accomplish this, he quits his job at his father's publishing company and transfers to Marukawa Publishing. But instead of being placed in their literary division, Ritsu finds himself working as the rookie manga editor for the Emerald editing department, a team that operates under extremely tight schedules in order to meet deadlines. There, Ritsu is introduced to the infamous editor-in-chief Masamune Takano, a persistent man who strives for results. As it turns out, Takano is actually Ritsu's high school love, and it is the aftermath of that heartbreak has caused Ritsu's reluctance to fall in love again. Now with the two reunited after several years of separation, the reestablishment of their relationship is marked by Takano's vow to make Ritsu say that he loves him again. Sekaiichi Hatsukoi follows three couples that are interconnected within the manga industry, with each being subject to the budding of first love.

High school biology teacher Tetsuo Takahashi may look like your average everyday instructor, but beneath his gentle appearance lies something less ordinary: his fascination for the "Ajin," more commonly known as "Demi." Although these half-human, half-monster beings have integrated into human society, Takahashi believes that much about them will remain unknown unless he interacts with them firsthand. Demi-chan wa Kataritai follows Takahashi's daily life in Shibasaki High School together with his three Demi students—Hikari Takanashi, an energetic vampire; Kyouko Machi, a gentle dullahan; and Yuki Kusakabe, the shy snow woman. Along the way, Takahashi also meets fellow teacher Sakie Satou, a succubus with an aversion towards men. To fulfill his goal of learning more about the Demi, Takahashi decides to conduct casual interviews with the girls to learn more about their abilities, psyche, and interaction with human society. As Takahashi strengthens his bond with his students, he soon discovers that the Demi are not as unusual as he initially believed. [Written by MAL Rewrite]

In a dystopian future where Japan's political organization has crumbled after the Great Tokyo War, Japan is broken up into 10 independent nations, with each nation controlled by a gang led by a "Best," a human-proclaimed prophet with destructive superpowers. Nozomi Moritomo is a "Rest"—a normal girl that has just started out as a rookie in the local gang. She wants to help the Best Masami Utoku, her childhood friend and role model, in the ongoing territorial dispute. When Masami becomes severely injured and unable to fight, Nozomi decides to go on a mission to complete the requests sent to Masami from all over Japan. Along the way, she meets Yukina Kosaka, a shy girl with no sense of direction; Ai Hibiki, an upbeat girl who loves eating; and Chiaya Misono, a quiet and mysterious girl that wears a gas mask. Together, the four girls travel all over the country on their motorcycles while getting involved in territorial wars, disagreements, and even suspicious conspiracies. [Written by MAL Rewrite]