After the demise of the demon king, the resulting power vacuum has broken the balance of the world. Eager to claim this power for themselves, self-proclaimed demon kings from various worlds assemble in the New Principality of Lithia to fight for it. Among them, master swordsman Soujirou Yagyuu seeks to take this coveted position for himself. Joined by Tooi Kagizume no Yuno, a young girl he saved from an army of golems that destroyed her city, Soujirou enters Lithia to battle his way to the title. At the same time, the leaders of the Aureatia Kingdom seek to destabilize Lithia by launching bandits after the convoys of merchandise transiting through the principality. Enraged, Imashime of Taren, the founder of Lithia and defector from Aureatia, sends vicious thief Kasasagi no Dakai to investigate the origin of these attacks. With war on the brink of eruption, no one can predict what influence the contenders for the demon king's throne will have on the coming conflict.

In the year Future Century 0060, the many countries that once comprised Earth's surface exist as separate colonies floating in space. Their home planet now uninhabitable, the ruler of all of the colonies is decided by their unanimous participation in the intergalactic Gundam Fight Tournament—a series of battles between the champions of each colony to determine who is most fit to reign over them all. Neo-Japan's champion is Domon Kasshu, a man who accepts the role with some ulterior motives. Domon searches the galaxy for his brother, a criminal who allegedly murdered their mother and made off with the Devil Gundam, a highly advanced weapon with the power to unleash mass destruction across the galaxy. In his quest to bring his sibling to justice, Domon travels from colony to colony, meeting many of the fighters who will become his allies and enemies in the forthcoming Gundam Fight Tournament. Armed with the strength of the Shining Gundam, Domon battles to uncover the truth behind his tortured childhood, suffering great betrayal and crushing blows on his quest toward personal and national triumph.

Yachiyo Inugami, a cat-loving extrovert, and Suzu Nekoyama, a dog-loving introvert, are unexpectedly cast into a relationship on a day like any other. The pair find themselves drawn together through an inexplicable attraction of their opposite personalities. As they quickly begin to understand one another, Inugami's hardened resolve to gain Nekoyama's favor only leads to frenzied responses. Soon after their momentous union, the two begin to spend more time with one another, growing closer all the while. Their combined antics gain the attention of the mousy Mikine Nezu, a classmate of Inugami, and soon they join the biology club. There, they meet Ushikawa Ukiji, a passive, cow-like upperclassmen. Nezu and Nekoyama soon begin to build upon their relationship and a game of cat and mouse soon begins. Wild, explosive, and vibrant, Inugami-san to Nekoyama-san tells the comedic tale of two high school girls and their less-than-normal relationship.

Ikebukuro is home to many different businesses and gangs. This includes Makoto Majima: the infamous troubleshooter who mediates between warring factions. Makoto knows all of the ins and outs of the bustling Tokyo district and strives to maintain peace alongside the G-Boys, who assist Makoto in his troubleshooting endeavors. Led by the charismatic and ruthless Takashi Andou, the G-Boys is the most influential gang in all of Ikebukuro. However, when the new faction Red Angels begins to move in on the G-Boys' turf, immediate tensions rise between them. With numerous enemies scattered around and within the G-Boys, navigating through the streets becomes more difficult for Makoto. While continuing to troubleshoot problems, he slowly unravels a plot that may trigger an all-out war and threaten the entirety of Ikebukuro.