The story is from manga volume 23.

Based on a manga by Mitsunaga Yasunori, serialised in Monthly Shounen Sirius. Hiyorimi Hiro moves to a new city to live with his older sister, but dies before he can find her. He then awakens to a new life as a servant of a Princess of the Monster Realm, who just happens to be employing his sister. Monsters soon appear to attack or pester the princess since she is in line for the royal throne, and Hiro must protect her with his life (and repeated deaths).

Bonus episodes 3.5, 6.5, and 9.5 included with the Blu-ray/DVD releases.

"Bobby really does little else but work on his bike. He cleans his bike. He tunes up his bike. He rides his bike. One would call him a motorcycle otaku. His most recent achievement seems to have been getting photos of himself on a road trip printed in a motorcyclist hobby magazine. This leads to an unexpected result: a girl his age, who picked up that issue on a whim, decides to write him a letter. A long, rambling letter, but dreamily romantic just the same. Bobby admits to his sister that he's never gotten a letter from a girl before. He writes back, "I got your letter. I'm happy cause it was from a girl." The "Bobby" referred to in the title is actually 17-year-old Akihiko Nomura, an underachieving high school kid with a deep love for motorcycles. His grades are failing, and his father – traditional and strict (but who must have also at some point gave in and allowed him to have a motorcycle) is trying everything he can think of to get the kid to apply for college. His mother is so silent, she might as well not even exist. Really, his support system lies entirely in his twinkle-toed little sister, who's nosy but cheers him on in her own way."