Every girl is a mystery when you're a 16-year-old boy, but Mikoto Urabe is in another league. She carries scissors hidden in her panties. She sleeps on her desk every day. She seems to have no friends whatsoever. But none of that can compare to what happens when Tsubaki Akira decides on a whim to taste a drop of her drool while Urabe sleeps. From that moment onward, things between Urabe and Akira are never the same, and the mysterious girl slowly becomes Akira's mysterious girlfriend. Along with their friends Ueno Kouhei and Oka Ayuko, Akira and Urabe try and navigate the minefield of high school first romance and all the strange things that happen along the way.

Keitaro has finally passed the entrance exams, and is officially a Toudai student. But after breaking his leg in an accident in the entrance ceremony, he thought and re-evaluated himself. Having new goals, Keitaro follows Seta on an overseas archeology trip. During his absence, however, all was not well in Hinata Lodge. Urashima Kanako, Keitaro's sister, arrives on the scene. She claims to be the new manager of Hinata Lodge starts to go against all the tenants. Things become even more complicated when they recieve a letter from Keitaro. The tenants and Kanako made a big mess trying to get the letter, but Seta's car crashes in before anyone could read the letter...

The world is in the midst of the industrial revolution when horrific creatures emerge from a mysterious virus, ripping through the flesh of humans to sate their never-ending appetite. The only way to kill these beings, known as "Kabane," is by destroying their steel-coated hearts. However, if bitten by one of these monsters, the victim is doomed to a fate worse than death, as the fallen rise once more to join the ranks of their fellow undead. Only the most fortified of civilizations have survived this turmoil, as is the case with the island of Hinomoto, where mankind has created a massive wall to protect themselves from the endless hordes of Kabane. The only way into these giant fortresses is via heavily-armored trains, which are serviced and built by young men such as Ikoma. Having created a deadly weapon that he believes will easily pierce through the hearts of Kabane, Ikoma eagerly awaits the day when he will be able to fight using his new invention. Little does he know, however, that his chance will come much sooner than he expected... [Written by MAL Rewrite]

In the warmth of a golden sun, timid high school student Haruka Suzumiya confesses to Takayuki Narumi, the boy she admires. Takayuki accepts Haruka's confession and the two become a couple, supported by their mutual friends Mitsuki Hayase and Shinji Taira. All is well for these friends—until tragedy strikes. One of them is sent to an unenviable fate, lying dormant in a coma. Three years later, they awaken, but their sudden reappearance in everyone's lives threatens to test the limits of these friends' bonds. [Written by MAL Rewrite]