The people of the kingdom look down on the young Prince Bojji, who can neither hear nor speak. They call him The Useless Prince while jeering at his supposed foolishness. However, while Bojji may not be physically strong, he is certainly not weak of heart. When a chance encounter with a shadow creature should have left him traumatized, it instead makes him believe that he has found a friend amidst those who only choose to notice his shortcomings. He starts meeting with Kage, the shadow, regularly, to the point where even the otherwise abrasive creature begins to warm up to him. Kage and Bojji's unlikely friendship lays the budding foundations of the prince's journey, one where he intends to conquer his fears and insecurities. Despite the constant ridicule he faces, Bojji resolves to fulfill his desire of becoming the best king he can be.

A treasure chest of unspoken courage is opened. The special is described as a collection of shorts, showing past instances of courage and personal growth by the cast of Ousama Ranking. (Source: Ranking of Kings Wiki)

The story is set before the main story's Battle in Nagoya arc. The Shinoa Squad receives another mission from Guren; to rescue a human girl named Riko from a mysterious vampire, Shahar, and bring her back to her family. However, Ferid and Crowley also appear when they find Shahar. Can Yuuichirou save the girl? (Source: Crunchyroll)

With the appearance of a mysterious virus that kills everyone above the age of 13, mankind becomes enslaved by previously hidden, power-hungry vampires who emerge in order to subjugate society with the promise of protecting the survivors, in exchange for donations of their blood. Among these survivors are Yuuichirou and Mikaela Hyakuya, two young boys who are taken captive from an orphanage, along with other children whom they consider family. Discontent with being treated like livestock under the vampires' cruel reign, Mikaela hatches a rebellious escape plan that is ultimately doomed to fail. The only survivor to come out on the other side is Yuuichirou, who is found by the Moon Demon Company, a military unit dedicated to exterminating the vampires in Japan. Many years later, now a member of the Japanese Imperial Demon Army, Yuuichirou is determined to take revenge on the creatures that slaughtered his family, but at what cost? Owari no Seraph is a post-apocalyptic supernatural shounen anime that follows a young man's search for retribution, all the while battling for friendship and loyalty against seemingly impossible odds.