It could also be that that's the reason the eldrich god is so interested in him, if mc was a yesmen who consented to everything then it'd be boring, may as well end the world now..
Now this could just be cope from my side, but i think it makes a bit of sense.
A good thought - I think part of it also would involve how they met in the first place, either pre- or post-Outbreak.
MC mentions that the first Cracks appeared 16 years ago, and on the day both he and Aru were born; and that 6 years before the present, the Outbreak occurred, and Aru was ...I guess "born".
Since it seems most people died once infected, I'm guessing Aru was infected (since she's described as half-human), but survived - and the question becomes if she's Aru the Human who's housing an eldritch being, or if Aru is
now the eldritch being and the human girl has been erased, or if they're both in there, and the Aru we see is the eldritch being but possesing Aru the Human's memories, personality, quirks, hopes & dreams, and so on.
And, did MC and Aru know one another beforehand? Or did they only meet post-Outbreak/Infection? And
how did they meet, if the latter? Almost no one knows who Aru really is (naturally), so I think a big part of what we need to know involves actual backstory for them both, and arguably both in terms of them as individuals and them as a pair.
But it's also only chapter 3, and I think this author's body of work speaks to her ability to write - so I'm happy to be patient and see what we learn as the story unfolds. Just lots of questions in the moment about the setting and the characters, because at face value MC's demeanor and behavior feel (more than) a bit incongruent with his circumstances at large.