The Mikadono sisters—Miwa, Niko, and Kazuki—stand at the pinnacle of Saika Academy as its Three Royals, renowned respectively as prodigies in shogi, karate, and theater. Unfortunately, they have drifted apart from each other due to their overwhelming dedication to their fields, effectively turning them into strangers living under the same roof. Enter Yuu Ayase, the son of the late Subaru Ayase, a legendary actress who graduated from Saika. Unlike his mother, Yuu lacks any extraordinary talent whatsoever, much to the disappointment of those who knew her. Still, he transfers to her alma mater with one quiet promise in his heart: to fulfill her final wish that he build a true and happy family. It just so happens that the Mikadono patriarch is also Subaru's longtime friend and benefactor, and he offers Yuu both a place to stay and a fresh start. Thrust into the lives of three estranged sisters who act cold toward him, Yuu may not be a genius himself, but the clumsy sincerity he brings might be what they all need to start anew.

As novelist Fuji is returning home in a rainstorm, her attention is caught by something peculiar: an animal resembling a dog asking her to take it in. Although she is reluctant at first, the animal impresses her by handing her an umbrella, resulting in Fuji welcoming the creature into her apartment. Soon, Fuji realizes that the animal is even smarter than she initially thought, as it begins communicating with her through writing. Whether the two are alone or hanging out with her family and friends, Fuji's new little friend never fails to entertain with its whimsical actions.

Lily Baker, a young English girl, decides to go to an arcade on Valentine's Day. She is determined to win a stuffed animal from a claw machine; but even after attempting it for hours, she is unable to get her hands on the prize. Just as she is about to give up, arcade employee Renji Kusakabe steps in and wins the prize for her as a present to celebrate the special day. Due to her cultural background, however, Lily mistakes his action as a declaration of love! With Lily returning to the same arcade in the hopes of seeing Renji again, the two begin exchanging a notebook to learn more about each other and their respective cultures. This marks the start of a friendship filled with gaming, but that is not enough for Lily, as she swears to make Renji fall in love with her!

Surrounded by four armies of dark beasts, five humanoid races strive to push the known boundaries of the world. Unfortunately, the 13 heroes dispatched to the southern region are easily wiped out by Clevatess, one of the Lords of Dark Beasts. Determined to get revenge against humanity, Clevatess bursts into the capital of the Kingdom of Hiden, leaving a trail of death and destruction behind him. Although the situation looks desperate, humanity still has a chance to appease Clevatess' anger. Alicia Glenfall, one of the 13 heroes, is revived by Clevatess to help him raise a newborn infant, Luna, whose choices shall shape the fate of the human world. Although reluctant to help the dark beast at first, Alicia understands that Luna is the only thing that stands between humanity and complete annihilation. Hiding himself by taking on a human form, Clevatess sets out in search for a wet nurse with Alicia and Luna. With Clevatess unwilling to reveal his identity, it falls on Alicia to slay all enemies that stand in their way. Meanwhile, the neighboring countries prepare to advance on the weakened Hiden, aiming to control the only forge capable of producing the heroes' weapons.