To prepare for reincarnation in another world, Kelvin gives up select memories from his previous life in exchange for powerful abilities, additional skill points, and an S-class summoner title. As a bonus, the goddess facilitating his rebirth, Melfina, offers him a choice of any companion to give him a head start in his summoner role. Kelvin—who has fallen head over heels for Melfina at first sight—promptly chooses the deity, confident that his passionate feelings for her will resurface even without all of his memories. Kelvin embarks on his exciting new journey with Melfina as his guide. However, in order to summon his beloved goddess' physical form, he needs to acquire significant amounts of mana points—and the best way to accomplish this is to level up by fighting strong enemies and making contracts with even stronger companions.

Having died in a car accident, Tsubasa Kurata—an otaku from modern Japan—is reborn in the Fremmevilla Kingdom, a medieval world where powerful mechs called Silhouette Knights are used to fight horrific demonic beasts. Born into a noble family under the name of Ernesti Echevarria and bestowed with prodigious magical abilities, he enrolls into Royal Laihaila Academy. This school of magic trains young men and women on how to pilot the Silhouette Knights, prepping them to protect the kingdom from threats, both demonic and human. Ernesti teams up with the twins named Adeltrud and Archid Olter with the goal to create his own Silhouette Knight one day, a feat unheard of for several centuries. [Written by MAL Rewrite]

The year is 2027, and the city of Kyoto has undergone tremendous technological advancement. Within the city lives Naomi Katagaki, a socially awkward and introverted boy with a love for books, and Ruri Ichigyou, a girl with a cold personality who is often blunt with people, but shares his love for reading. Despite having similar interests, Naomi is afraid to approach Ruri due to her unfriendly nature. One day, as Naomi goes out for a walk, a crimson aurora pierces through the sky for a brief moment before vanishing. Shortly after, he sees a three-legged crow and a mysterious hooded man who reveals himself to be Naomi from 10 years in the future, explaining that he has come to change an imminent tragic event that happens to Ruri shortly after they start dating. Initially taking his words with a grain of salt, present-day Naomi follows his future self's instructions and starts getting closer to Ruri, determined to save her. Hello World focuses on the present Naomi alongside himself from 10 years into the future. With the help of his future self, Naomi begins his preparations to save Ruri. Will he be able to change the future? [Written by MAL Rewrite]

As a young child, Aizawa Yuuichi had often visited his cousin in the city; however, something drastic happened to keep him away for seven long years. Now, Yuuichi returns, his memories of those days are simply gone. Settling into the wintry town, Yuuichi comes across several young girls, all of whom are connected to his past. As he befriends them and continues to interact with them, the long forgotten memories from his childhood begin to resurface... [Written by MAL Rewrite]