On Christmas Eve, four-year-old Miri Unasaka arrives in Tokyo completely alone, in search of her father. The bright lights and merry atmosphere guide Miri to a big hotel and a man with a delicious-looking cake. However, the child has just unknowingly walked into the center of an elaborate, foolproof plan for assassinating a dangerous mafia boss. Professional assassins Kazuki Kurusu and Rei Suwa live together, fleeing memories of their grim childhoods and avoiding emotional connections. When their mission goes awry and they end up bringing Miri home, there is only one reasonable thing to do: return Miri to her mother. But the girl's innocent laugh and pure worldview quickly enamor her to Kazuki, who secretly enjoys playing a parent, and it is not long before Rei's impenetrable heart makes room for Miri. Miri's every move is unpredictable, and Kazuki and Rei find raising an energetic child harder than any of their missions. Although it presents a great risk to their careers, Kazuki and Rei—both assuming the affectionate nickname papa—decide to provide Miri with a normal childhood despite all the odds stacked against them.

It's been a year since the disappearance of Shiro, the Silver King; Kurou Yatogami and Neko have been diligent in their search, but to no end. Their investigation leads to a run-in with members of the now disbanded Red Clan HOMRA—Rikio Kamamoto and Anna Kushina—being pursued by the Green Clan, who desire Anna's powers for their own ends. Now, the members of Scepter 4 are called upon alongside Kurou and Neko in order to rescue Anna, the mascot, and only female member of the ruined Red Clan, from the enemy's clutches and hopefully find Shiro using the young girl's powers. Amidst crisis, the group is forced into a power struggle when the Green Clan threatens to overtake the Gold King's domain. The second step in the K Project series, K: Missing Kings, continues the story of a young boy caught up in a psychic war between seven kings, and showcases each character's struggles after the losses of their respective Kings.

No longer concerned with military affairs, Yukichi Fukuzawa intends to act as a lone bodyguard-for-hire, making use of his deadly swordsmanship. However, things are not going as planned for his freelance business, and that is when he crosses paths with a mouthy boy named Ranpo Edogawa. While their initial interactions are intertwined with a bizarre murder mystery, the aftermath prompts the formation of the Armed Detective Agency. Presently, Ranpo finds himself chasing down a gifted individual with the dangerous ability to execute the perfect crime. But as the great detective unravels the case, he soon discovers an elaborate plot to obliterate the Agency in its entirety. Although forewarned of the trap, the Agency continue their pursuit of the criminals, only to end up framed for the crime themselves. Now branded as wanted terrorists, the remaining members must find a way to prove their innocence—even if they must turn to sworn enemies for assistance.

Vampires walk among society, existing as part of its underbelly. They do not require blood to survive, but extreme emotions can immensely increase their bloodlust, turning them into uncontrollable monsters. Tsukasa Taira, a 22-year-old university student, learns of the existence of vampires when her longtime friend reveals himself to be one of them after a tense confrontation with Yuuki Anzai—a human and vampire hybrid. Her friend is arrested, and Tsukasa soon finds herself drawn to Anzai, who reluctantly reciprocates her feelings. However, this unconventional romance may prove too difficult to maintain, as Anzai struggles to contain the part of him that wishes to devour Tsukasa.