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If you look at this on zenon comics, you could see the Bloody Love emphasis. This might not be yaoi, but it is BL. And the ending at chapter 40, Yamadera made Sayo drink his blood in public, while on his mind he wants the world know that Sayo is his. Laude even offered him to turn him into a vampire and Yamadera doesn't accept the offer because that means he will be losing Sayo.
Yamadera is crazy, but I think he likes Sayo (even though he won't admit it).