>>281192691Rather than "all of them are bisexual," I think that series is actually making a point that sexuality doesn't exist and people without any kind of knowledge of normalcy will submit to carnal desires regardless of what sex their partner is. The reason Maria gives for leaving Saki is that they can't have a baby together, because it shows a shift in her from just carnal desire to desiring a family, which represents growing up. Shinsekai Yori is very much about what humans are like in their base form, by genetics alone, vs. how society shapes people. (That's also what the actual main plot about the bakenezumi is about)