Souta Takatsuki and his neighbor Rikka Amanome have been like brother and sister since they were kids, but his feelings for her run much deeper. With her birthday coming up, he wants to find the perfect gift, which presents itself in the form of a book from a mysterious shop he happens across. The owner doesn't even charge him, saying he'll return to pay eventually...Souta is wholly unprepared for the insatiable passion the book inspires in Rikka, and it seems the ultimate price of this gift may be hefty indeed...

After Makoto’s confession, Souta finds himself having to balance a delicate three-way relationship. Trying to keep both lust-crazed girls satisfied while also keeping his cheating a secret from Rikka is hard enough, but Zepar isn’t through with him yet…as the next to fall victim to her curse is none other than their homeroom teacher, Tateaki-sensei! Faced with the domineering charms of a lonely adult woman, will Souta be sucked into yet another immoral affair?

Souta and Rikka are officially boyfriend-girlfriend, but they still haven'tbroken the demon Zepar's curse. Then, one day, Makoto, who had seen Rikka's"grimoire," falls prey to the curse herself. She consults with Souta and theybegin to have a side relationship to keep Makoto's symptoms under control. Butthen Makoto leans into her curse and doesn't even want to be free of it?! Whenthe grimoire's curse catches Makoto in its clutches, Souta, Rikka and Makotoform a love triangle?!

Two years have passed since Zenjiro was summoned to a kigdom in another world and married its beautiful queen. Now, Zenjiro and Queen Aura celebrate the birth of their child--the young First Prince of Capua---and the realm celebrates with them. Yet while Zenjiro is busy adjusting to his new life as a father, a bloody massacre breaks out along the vital Salt Road. A company of knights and warriors rides to do battle with all manner of wyverns, even as a delegation arrives from the Twin Kingdoms with an agenda all its own!

"Your secret now belongs to me." Welcome to Murakumo Inn, a curious establishment that opens its doors to the troubled masses, human or otherwise. But to pay for the stay, the equally curious innkeeper takes payment only in the form of one's deepest secrets...Who will come calling today?

After Hanabi is heartbroken, she goes to Karuizawa with Ebato. This journey is guiding the two towards an end to their relationship. Elsewhere, even after Mugi conveyed all of his feelings to Akane, the free spirited girl didn't reply in kind. Who is the one that holds the keys to her heart?

Analyzes the feelings and problems involved in different types of human love, including familial affection, friendship, passion, and charity.