5. Owari no Seraph
Synopsis: A mysterious virus appears out of nowhere, killing anyone above the age thirteen. Vampires appear, enslaving the young ones by promising to protect them in exchange for their blood. These survivors include Yuuichirou and Mikaela Hyakuya, two young boys from an orphanage, along with other children. Tired of being enslaved to vampires, Mikaela forms an escape plan, which failed in the end. The only survivor is Yuuichirou, who manages to escape to the outside world. He joins the Moon Demon Company, a unit formed to eliminate the vampires in Japan.
Similarities: Before their own eyes, the main characters lose their family (Rin lost his father, Yuuichirou lost Mikaela and the other children). Haunted by this moment in time, unable to do anything, they join a setting dedicated to eliminating their enemies.
4. The Devil is a Part-Timer!
Synopsis: The Demon Lord Satan starts his quest to conquer Ente Isla with his demon army. Unfortunately for Satan, his plans fell apart when the hero, Emilia, appears. Her appearance forces Satan to retreat with Alsiel into a portal that led them to the human world. He vows to someday return to Ente Isla to complete his quest, if they can find their way back. *Note: Satan and Lucifer are different people in this anime!*
Similarities: Both series involves around a character that isn’t fully human living on Earth. Through them being different, they are able to learn more about themselves and the world (as Rin didn’t know demons existed until recently). There is also the fact there are parallel worlds in both series, one of humans, and one of demons.