Sekai-ichi Hatsukoi: The Case of Ritsu Onodera (世界一初恋 〜小野寺律の場合〜, Sekai-ichi Hatsukoi ~Onodera Ritsu no Baai~) is the first volume of the Sekai-ichi Hatsukoi manga series. The volume is released as The World's Greatest First Love: The Case of Ritsu Onodera in English by SuBLime.
- The Case of Ritsu Onodera No.1
- The Case of Ritsu Onodera No.2
- The Case of Ritsu Onodera No.2.5
"The Case of Ritsu Onodera No.1" introduces Ritsu Onodera as he begins his new job at Marukawa Publishing. Ritsu has left his literature editing job at his father's company to work where he won't be accused of receiving favoritism. Although he applied to edit literature at Marukawa, he is instead assigned the shoujo manga department Emerald where he meets his new boss Masamune Takano. After seeing the stress of editing a monthly manga magazine, including being kissed to pose for a mangaka and pulling an all-nighter, he discovers that his new boss is his first love from high-school. Realizing that their breakup was a misunderstanding, Takano becomes determined to get Ritsu back, but Ritsu is determined to focus on his career and rejects him. The chapter ends with Ritsu realizing that the neighbor he's never met is Takano.
In "The Case of Ritsu Onodera No.2," Ritsu begins managing his own author, Yukina Mutou. The chapter begins with Takafumi Yokozawa yelling at Takano for under-printing a book that's sold-out, but Ritsu later sees them chatting and laughing together and becomes jealous. That night, Ritsu goes over Mutou's manuscript but he isn't sure about his edits, so Takano insists he come over and they go over the manuscript together. Afterward, Takano comes onto him, but Ritsu grabs the manuscript and flees, only to run into Yokozawa at the door. Later, Mutou's assistants all fall ill and Ritsu flies to Hokkaido to help finish the manuscript, and he manages to get the manuscript back in time for printing. Ritsu is so exhausted that he falls asleep next to Takano on the train home. He wakes up next to Takano in bed, asks if anything weird happened, and runs out.
"The Case of Ritsu Onodera No.2.5" begins during Ritsu and Takano's (then named Saga) high-school days, when Ritsu first fell in love with him. After Ritsu confesses to him in the library, Saga says they'll go out together and invites him back to his place where they end up having sex. The chapter ends in the present day with Takano yelling at Ritsu to wake up because he's fallen asleep at work. Takano points out that Ritsu looked really happy so he must have been dreaming about something nice, but Ritsu defensively insists it was a terrible dream and gets back to work.
- Ritsu Onodera
- Masamune Takano (formerly Masamune Saga)
- Shouta Kisa
- Kanade Mino
- Yoshiyuki Hatori
- Takafumi Yokozawa
- Yukina Mutou