Abruptly catapulted into a fantasy world, Mimori Touka and his classmates have been summoned by the world’s resident goddess to serve as heroes. Luckily, most of the students display amazing skills upon arrival—except for Mimori, whose abilities bottom out at a measly E-rank. With no further use for him, the goddess banishes Mimori to a dungeon from which no one has ever returned alive. Yet, as it turns out, Mimori’s skills aren’t so much worthless as they are abnormal. Abnormally powerful, even. If Mimori can only claw his way back to the surface, nothing will stand in his way from getting revenge.

The manga tells the story of Mira, who leads an evil organization trying to take over and destroy everything. Earth is under attack, but a magical girl named Byakuya Mimori stands up to Mira's group. As they face off, something unexpected happens—Mira falls in love with Mimori.

Kazuhiko Nukumizu, a self-proclaimed "background character," accidentally witnessed his popular classmate Anna Yanami being rejected by her childhood friend. Since then, Kazuhiko has become involved with several loser heroines, including Anna.

Jun Shirasaki and the Jinguuji sisters are childhood friends and neighbors. When Jun's first girlfriend, the older sister Ryuumi, breaks up with him, she says something that complicates the three people's relationship, their first loves, and their romance—?