I often see “realism” used as an excuse to justify things which would make stories less enjoyable for minority readers. It should be remembered that these are as much games as they are stories, and forcing one particular subset of readers to have a much worse time is unfair, no matter how “realistic” it might be. Besides, as @komorebi pointed out, this isn’t the real world, so why wouldn’t it be realistic for everyone to be bi?
(I actually made quite a long post about this some months ago, if you want to see more arguments…)
Pls don’t kill Clyde… 
Or make him hate us for our blood colour… Or kill Alyssa and have him blame us and hate us for that…
(Although, if you do kill Clyde, I would consider it kinda disingenuous, since you’ve been treating him as an RO thus far… I’m not a big fan of dead boyfriends… 
)