Rentarou Aijou has it all: looks, intelligence, athletic skill, and popularity with peers and mentors alike. Unfortunately, none of these qualities help Rentarou with his love life. On the day of his middle school graduation, he is once again turned down by a girl he confesses to, earning his one-hundredth rejection in a row. Down on his luck, he goes to a matchmaking shrine and wishes to finally get a girlfriend in high school. When the god of the shrine suddenly appears before him, Rentarou is told he will meet an astronomical total of one hundred soulmates in high school. Though Rentarou initially does not take this foretelling seriously, his doubts disappear when, on the first day of school, he meets two of these soulmates—Hakari Hanazono and Karane Inda—who both confess to him. With fated encounters and love confessions galore, Rentarou's life is about to get a lot more exciting.

Mahiru Kouzuki, a skilled artist, gives up on her passion after her elementary school classmates ridicule her colorful jellyfish mural. Several years later, upon encountering an unexpected admirer in Kano Yamanouchi—a former idol with a troubled past—Mahiru decides to pursue her childhood dreams once more. Tasked with designing the mascot for Kano's new music project, JELEE, Mahiru enlists the help of her childhood friend and professional streamer Kiui Watase to make JELEE's first music video. Together with Kim Anouk Mei Takanashi, a pianist and fan of Kano's work as an idol, the girls aim to turn JELEE into a global hit. However, if they want to succeed in this ambitious endeavor, they will first have to free themselves from the shackles of their pasts.

After the climactic battle to decide the fate of humanity, the hero Max, alongside his party, emerges victorious against the formidable Demon Lord. As he draws his last breath, the defeated Maou vows to return more powerful than ever to take his revenge. Ten years later, although Maou has resurrected, the process is incomplete, resulting in him taking on the form of a child. Nevertheless, not wanting to waste another second, Maou pays his nemesis a visit—but the hero who once gallantly protected humankind from the demon's clutches is now a pitiful slob bearing no resemblance to a man of his former caliber. Despite his disappointment, Maou moves in with Max in hope of building him back up into a worthy adversary. But as the demon learns more about the events that transpired in the decade of his absence, he realizes that there is a story behind Max's downfall that he knows nothing of.

Second part of Houkago Shounen Hanako-kun.