So I'm guessing what happened is that in the original timeline, Miri (Little sister) went to America to test whatever machine they had, and she died. Not just disappeared died. She only disappeared that one chapter because what we see in the manga is Ritsu running a supercomputer simulation...
Guide failed to see the bigger picture because he was too focused on the negative emotions and failed to notice the positive emotions of the frontier fleet towards Liam.
MC looks like the MC from Fukushuu o Koinegau Saikyou Yuusha wa, Yami no Chikara de Senmetsu Musou Suru. So much so he is immediately giving off creepy vibes. :shamihuh: