The relationship between Nagi and Genkaku has lots of Ho Yay (also overlapping with Foe Yay). It starts off a bit more subtle, with Genkaku seeming a bit too intense and obsessed with getting Nagi to join the Undertakers (along with an interrogation scene between the two, where Genkaku is shown licking the blood from Nagi's arm and calling Nagi "cute"). Later, however, the Ho Yay levels go through the roof when Genkaku is shown getting incredibly turned on by Nagi killing some poor sap, saying that Nagi is a "red flower that has bloomed." After that, he later pretty much gives Nagi a love confession telling him that the murderous side of him was beautiful and exquisite, and that he loved him. And that's not even mentioning how annoyed and angry Genkaku gets whenever he sees the possibility of a girl getting close to Nagi (in regards to Shiro, he is shown being extremely agitated, wondering what relationship she has with Nagi, and saying that Nagi never learns. In regards to Karako, he stabs her when she hugs Nagi, telling her, "Don't touch my carnage, you shitty girl"). And later, Nagi does a double suicide with Genkaku, holding him down so Ganta can kill him. Genkaku appears extremely happy, and calls Nagi his "savior" (instead of attributing it to Ganta, which would actually make more sense, considering Ganta is the one that kills him). Ah well, he's just biased that way.