A dark knight named Erlink suddenly transferred into Kurama Keiji's school. Before they noticed it, she had fallen in love with Keiji and Keiji had fallen in love with her armor. But like it often happens, thinking that Keiji liked somebody else, she took off her armor and transformed into a different person in order to visit Keiji's house and keep watch over him. While the wild Eri feels happy to live with Keiji, play with Keiji and eat with Keiji, they grew closer…

"Keiji, won't you eat me?"

"What do I look like to you, some kind of titan or zombie?"

The love story of a dark knight in his living room begins here!