Deep in the forest, far from any human contact, there lives a child named Ryouma Takebayashi. He engages in the rather strange hobby of keeping various types of slimes as pets. Furthermore, despite his young age, he has a sturdy physique and good compatibility for magic. All of this is because, having endured much hardship in his previous life, three gods grace Ryouma with a second chance to pursue one goal: savor the wonders of life. After three years of comfortable solitude pass by, Ryouma meets people that will change his current life forever. When he encounters and helps some soldiers tend to their wounded comrade, the group convinces him to accompany them to visit the nearby town's ducal family. Ryouma agrees and soon embarks on a journey to explore the vast world beyond his home.

Since reincarnating into a new world, Ryouma Takebayashi has used his god-given graces to tame countless slimes and employ them to improve the lives of everyone around him. With the astonishing success of his laundry shop, Bamboo Forest, he is finally ready to take on new frontiers and open a branch in the neighboring city of Lenaf. Abiding by his promise with his dearest friend, Eliaria Jamil, Ryouma makes every day count, whether learning new techniques, forming connections, or even discovering more species of slime.

In her first life, the renowned and genius surgeon Dr. Aoi Takamoto was Elise de Clorance, a villainess of noble descent. Elise's selfishness, insolence, and obsessive love for her fiancé—Prince Linden de Romanoff—led to the deaths of her family members and, eventually, herself. Only after being reborn did Elise realize the error of her ways and decide that, instead of ruining lives, she would devote herself to saving them. But a tragic airplane crash robs her of her dreams too soon. By a miracle, Elise wakes up in her original body before her official engagement to Linden. Recognizing the chance to cherish her loving family and free Linden from an unwanted marriage, Elise wishes to use her advanced medical knowledge to continue down the path of saving lives. In a deal with the emperor, Elise is given only six months to prove that her true place is not on the throne, but rather with the wounded and ailing who desperately need her help.

Eighteen-year-old Dale Reki is a skilled, kind, and respected traveler, acknowledged as one of the leading adventurers in the city of Kreuz. One day while on the hunt for magical beasts, he comes across a sweet devil girl named Latina. She is alone, dressed in rags, and bears the devils' symbol of a criminal: a broken horn. Concerned for her wellbeing, Dale decides to ensure Latina's safety by bringing her to his home, eventually leading to him adopting her. Latina is sweet, innocent and compassionate, charming Dale beyond his expectations. He begins to enjoy the life of parenthood— experiencing the trials that come with raising a child and coping with the heartache he feels whenever his busy lifestyle as an adventurer parts him from her. Although work and life as a new parent become reassuring constants for Dale, the mysteries surrounding the girl remain. Why was Latina alone in the forest, and why does she harbor the symbol of a criminal? At the same time, Latina also begins to learn about the world and herself as she adjusts to her new life with Dale.