ser·aph
[ˈserəf]
NOUN
an angelic being, regarded in traditional Christian angelology as belonging to the highest order of the ninefold celestial hierarchy, associated with light, ardor, and purity.
Yuuichiro is a seraph, which according to Christianity, is associated with light and purity. But according to the world he lives in, people could care less about the definition of their species. Humans simply saw them as hideous winged creatures that they could do whatever they wanted to. They hunted them, killed them, took their wings, tortured them and did other unspeakable things to them. And Yuuichiro's beautiful and rare feathers resulted in much more pain than anyone should be able to handle or deserve.
vam·pire
[ˈvamˌpī(ə)r]
NOUN
a corpse supposed, in European folklore, to leave its grave at night to drink the blood of the living by biting their necks with long pointed canine teeth.
Vampires on the other hand were defined as more gruesome creatures, yet in the real world, they're treated as normal people. So, vampires like Mikaela live in a life of luxury while the seraphs are tortured and beaten mercilessly.
But what happens when a pair of the two species meet? Will there be more pain in Yuuichiro's future? Or will the vampires only bring happiness?
(Sadly, art is not mine and I don't own Owari No Seraph nor the characters; rated M for potential violence and sensitive subjects and crap)
Kanda Kyoichi transmigrated to Konoha and became a temporary instructor at the Ninja Academy. Fortunately, he awakened the Mentor System.
By teaching others, he could earn rewards.
Thus began Kyoichi's career as a "teacher" in the ninja world.
Shisui: "Sensei's unique interpretation of the Will of Fire has given the Uchiha Clan a true sense of direction!"
Asuma: "The essence of the jade lies in protecting the people, with the advanced leading the way for the less experienced. Only then can Konoha become stronger!"
Kakashi: "He's my life mentor. He transformed Konoha!"
...
Years later, in the memoirs of Kyoichi, now the Hokage, he wrote:
"I honestly just wanted to be a life mentor!"