Hmm not sure if I like this direction, that typical “I don’t trust you” plot is kinda stale to me. I bet the optimistic and hopeful younger sister is gonna die and the cynical brother will learn the meaning of friendship or something, then at the end of the arc he’ll set off to find more people like him, but it doesn’t make sense why he thinks he shouldn’t trust anyone when it sounds like they never met anyone else to begin with( maybe escaped from a lab?), anyway it just reeks of forced drama... We’ll see how it goes.