When Ryu returns to pay homage to his deceased mentor, Gouken, he is tormented by disturbing memories of his master's killer. In a quest to become a true martial arts master, Ryu sets out to hone his street fighting skills and to deliver himself from the haunting legacy of the Dark Hadou. But the ultimate test of his new power can only be accomplished through one last fateful confrontation with his arch-nemesis, Gouki (Akuma).

The charming incarnations of the seven deadly sins—brothers Lucifer, Mammon, Leviathan, Satan, Asmodeus, Beelzebub, and Belphegor—can never seem to keep out of mischief. They are demons feared across the Devildom, but, at the Royal Academy of Diavolo, one human transfer student has captured their collective hearts. Whenever the brothers miss them, they engage in ridiculous antics to keep themselves entertained, and they even drag others into their neverending shenanigans.

After harboring an unrequited love for years, Naoya Mukai finally gets to date his childhood friend, Saki Saki. However, just as he tries to commit himself to this relationship, he receives an abrupt confession from Nagisa Minase. At first, Naoya tries to reject her but is soon overcome by feelings of not wanting to hurt Nagisa. Trying to avoid betraying his girlfriend's trust in him, Naoya thinks up a "solution" to make both girls happy—two-timing. Naturally, Saki rebuffs this idea, but through Naoya's and Nagisa's persistence, she reluctantly submits. With this, a three-way affair begins between Naoya, his girlfriend, and his "other" girlfriend, as they develop a relationship that deviates from the social norm.

Shun Hashimoto is an openly gay aspiring novelist living in Okinawa who was abandoned by his parents after coming out to them. Mio Chibana is a reserved, orphaned high school student, often found spending his time by the sea. One day, the two meet on the beach, and Shun is instantly captivated by Mio. The days fly by as they slowly begin to grow closer until Mio suddenly announces that he has to leave for the mainland. Three years pass before a 20-year-old Mio returns to Okinawa to confess his love to Shun. However, in those three years, Shun's life has changed. Will he be able to accept Mio's feelings and make such a commitment?