Reeling from her recent breakup, Momo Ayase, a popular high schooler, shows kindness to her socially awkward schoolmate, Ken Takakura, by standing up to his bullies. Ken misunderstands her intentions, believing he has made a new friend who shares his obsession with aliens and UFOs. However, Momo's own eccentric occult beliefs lie in the supernatural realm; she thinks aliens do not exist. A rivalry quickly brews as each becomes determined to prove the other wrong. Despite their initial clash over their opposing beliefs, Momo and Ken form an unexpected but intimate friendship, a bond forged in a series of supernatural battles and bizarre encounters with urban legends and paranormal entities. As both develop unique superhuman abilities, they learn to supplement each other's weaknesses, leading them to wonder if their newfound partnership may be about more than just survival.

One night, as meteors streak across the star-studded sky, Shion Pavlichenko becomes a Contractor. Despite her brother's transformation, Shion's twin sister Suou continues to live a fairly ordinary life, attending middle school with her friends and getting caught up in the awkwardness of growing up. However, everything changes when her home is invaded by a masked man cloaked in black, destroying any sense of normality she once had. Revealed to possess latent Contractor abilities of her own, Suou is caught between family, friends, and her own sense of purpose as she ventures into the ruthless world of cutthroats and espionage that Contractors call home. Meanwhile in Tokyo, investigation surrounding Hell's Gate's sudden collapse is underway, and prophetic signs of doom point in the direction of a silver-haired doll.

Raku Ichijou, a first-year student at Bonyari High School, is the sole heir to an intimidating yakuza family. Ten years ago, Raku made a promise to his childhood friend. Now, all he has to go on is a pendant with a lock, which can only be unlocked with the key which the girl took with her when they parted. Now, years later, Raku has grown into a typical teenager, and all he wants is to remain as uninvolved in his yakuza background as possible while spending his school days alongside his middle school crush Kosaki Onodera. However, when the American Bee Hive Gang invades his family's turf, Raku's idyllic romantic dreams are sent for a toss as he is dragged into a frustrating conflict: Raku is to pretend that he is in a romantic relationship with Chitoge Kirisaki, the beautiful daughter of the Bee Hive's chief, so as to reduce the friction between the two groups. Unfortunately, reality could not be farther from this whopping lie—Raku and Chitoge fall in hate at first sight, as the girl is convinced he is a pathetic pushover, and in Raku's eyes, Chitoge is about as attractive as a savage gorilla. Nisekoi follows the daily antics of this mismatched couple who have been forced to get along for the sake of maintaining the city's peace. With many more girls popping up his life, all involved with Raku's past somehow, his search for the girl who holds his heart and his promise leads him in more unexpected directions than he expects.

Manji is an infamous swordsman in feudal Japan who is known as the Hundred Man Killer, as he has killed one hundred innocent men. However, there is something far more frightening than his ominous reputation: the fact that he is immortal. This is the handiwork of eight-hundred-year-old nun Yaobikuni, who placed bloodworms capable of healing almost any wound in Manji's body. To atone for his crimes, Manji resolves to kill one thousand evil men. Yaobikuni agrees to this proposal, saying that if he succeeds, she will undo his curse of immortality. Soon after this promise, Manji meets Rin Asano, a 16-year-old girl who requests Manji's assistance in killing those who slaughtered her parents. Initially reluctant, Manji refuses Rin's desperate plea. However, owing to her evident lack of strength, Manji changes his mind and agrees to protect Rin for four years. With this partnership set in stone, the two embark on a perilous journey of bloodshed, vengeance, and redemption, each to fulfill their own life's cause.