Sekai-ichi Hatsukoi (世界一初恋), or The World's Greatest First Love, is a Japanese BL series created by Shungiku Nakamura. It began as a manga and light novel series in 2006. In 2011, the manga was adapted into an anime television series, which includes portions of the light novel series as well. It's additionally been adapted into a drama CD series, and has additional content such as radio CDs and character songs performed by the anime voice actors.
The Case of Ritsu Onodera (小野寺律の場合, Onodera Ritsu no Baai) is the main story told in the manga series and the anime adaptation . It follows Ritsu Onodera, a literature editor, as he begins a new job in shoujo manga at Marukawa Publishing. His new boss, Masamune Takano, turns out to be Ritsu's first love from high school.
The Case of Chiaki Yoshino (吉野千秋の場合, Yoshino Chiaki no Baai) is the first light novel series. It follows mangaka Chiaki Yoshino and his developing relationship with lifelong friend and current editor Yoshiyuki Hatori, and the love triangle formed with Yuu Yanase, Chiaki's friend who also vies for Chiaki's affections.
The Case of Shouta Kisa (木佐 翔太の場合, Kisa Shouta no Baai) is a story told in the manga series beginning in 2009. It follows the relationship between Shouta Kisa, a shoujo manga editor, and Kou Yukina, a bookstore employee and fan of Kisa's work.
The Case of Takafumi Yokozawa (横澤隆史の場合, Yokozawa Takafumi no Baai) is the second light novel series which began publication in 2011. It follows the relationship between Takafumi Yokozawa and Zen Kirishima.