A sickly salaryman who always felt an unexplained internal heat collapses during a busy work period, only to be met by a goddess who explains he was born in the wrong world. The heat was magical power, but he was born in a world without mana. Through the goddess's power, he is reincarnated as Itsuki in a new world, granted the healthy body he always wished for along with abundant magical abilities. As part of his new beginning, he receives an egg that hatches into a legendary magical beast he names Shiro, a fluffy and adorable creature that becomes his contracted familiar and partner.

The core of the story follows Itsuki and Shiro as they embrace a slow, enjoyable life in this fantasy realm. They befriend a young merchant named Secelia, whom they rescue from danger, and travel with her to the city of Leirs. There, Itsuki registers as an adventurer at the guild, starting from F rank while Shiro passes a separate registration test to be officially recognized as his familiar. Their days are filled with cooking delicious meals, sampling city cuisine, and taking on quests. However, Shiro grows rapidly, and his increasing appetite becomes a running concern for Itsuki as food expenses mount.

Early narrative arcs involve Itsuki taking his first quests. After completing a goblin subjugation mission in a forest, they encounter a gluttonous slime creature named Bak, who joins their growing group of companions. With Shiro and the surprisingly powerful Bak by his side, Itsuki decides to leave Leirs and journey to a new city called Baldor to raise his adventurer rank and better protect his friends. Traveling with a party named Giant's Sword, the journey introduces new flavors, new landscapes, and the continued charm of Itsuki's affectionate and powerful fluffy companions.