Touya Mochizuki grows accustomed to his new life in another world. Armed with his trusty smartphone, the teenager accepts small quests at his leisure while spending time with his new fiancées: Yumina Urnea Belfast, Yae Kokonoe, and twin sisters Linse and Elze Shileska. But even in a relaxing environment, Touya is only beginning to understand the responsibilities that come with these engagements. In addition to his romantic woes, the elder fairy Lean wishes to locate the remaining pieces of Babylon, the floating island that the mysterious Professor Regina Babylon created five thousand years ago. Touya reluctantly accepts her request and seeks out the teleportation circles that will lead to the islands. However, strange monsters have emerged—possibly powerful enough to destroy the world. In order to save the second life he was given, Touya must weaponize ancient technologies to fight these monsters—all while balancing his overwhelming number of relationships.

The story begins in Anpanman World, where everybody is bustling around, getting ready for the annual Star Festival. On that day, an egg emerges from Baikinman's garbage box, and when it hatches, a mysterious boy named Kurun emerges from within. Though Kurun does not know where he came from, he spends his days having fun with everybody. But one day, black stars begin raining down. Anpanman thinks that something suspicious might be occurring at the Star of Life, and he heads there. (Source: ANN)

In search of a mystical ingredient known as Sky Fish, Meliodas and Hawk stumble upon a spring that suddenly transports them to the Sky Temple: a breathtaking land above the clouds, inhabited by beings called Celestials. Meliodas, however, looks strikingly similar to a local criminal called Solaad, and is imprisoned and shunned as a result. Meanwhile, the kingdom of the Sky Temple prepares to defend the Great Oshiro's seal—said to harbour a three thousand-year-old evil—from the malevolent Six Knights of Black, a group of demons who seek to destroy the seal. However, the Demon Clan is successfully unleashed and terrorizes the land, prompting the remaining Seven Deadly Sins and the Celestials to fight against their wicked foes. The battle progresses well, until one of the Six Knights awakens an Indura of Retribution, an uncontrollable beast from the Demon Realm. With its overwhelming strength and sinister power, the Seven Deadly Sins and Celestial beings must now work together to defeat the creature that threatens their very existence.

Despite completing all the tasks given to them, Ainz Ooal Gown, Tanya Degurechaff, Kazuma Satou, Subaru Natsuki, and the other members of Class 2 are surprised to find out that their role as students is far from over. With no means of returning home, the class of eccentric personalities is still mysteriously stuck in the unfamiliar world. Although, as they are becoming quite fond of each other, spending more time together does not sound that bad. With the unexpected arrival of new transfer students, the comedic antics of our beloved characters continue to grow. Thus, their bizarre yet nonchalant school life continues.