Each episode tells a different story from Grimm's Fairy Tales.

Struggling yet brilliant 19-year-old Minato Sahashi has failed his college entrance exams for the second time, resulting in him being regarded as worthless by those around him. However, the course of his seemingly bleak future is altered dramatically when a beautiful, supernatural woman falls from the sky and into his life. That woman, Musubi, is a unique being known as a Sekirei, a humanoid extraterrestrial with extraordinary abilities. These aliens are known for kissing humans carrying the Ashikabi gene in order to awaken additional latent powers deep within. Recognizing the potential within the seemingly insignificant youth, Musubi kisses the bewildered Minato, initiating a bond between the two of them. This drags him into the high-stakes world of the Sekirei, where he and his new partner must compete against others in a battle for survival called the Sekirei Plan. However, unbeknownst to the contestants, there is far more at risk that what the competition initially entailed.

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.

As luck would have it, on her first day at Holbein Entertainment Co., Miki Ishimoto is tasked with managing a brand new idol group! A recent college graduate, Ishimoto is eager to begin her career in the industry. However, her department's responsibility is...statues?! The statues in question are the Sekkou Boys, or The Rockies, a boy band comprised of four Greco-Roman sculptures: St. George, Mars, Hermes, and Medici. These four busts are new to the entertainment scene, and it is up to Miki to ensure the Rockies' prosperity in the idol world. But will they be a stone-cold success? Or will Miki's management prove to be a rocky start to stardom?