Although i want them to succeed in the rescue mission so we can be done with this garbage manga, i'm pretty certain they're going to fail by how sudden the rescue mission started. There was no real planning going on for multiple chapters or anything, it was just like ''oh i see the girl i like...
Even if they end up finding who and what he is, what exactly are they going to do about it? If they want to wage a war against him, then surely he is strong enough on his own to completely decimate their army.
I really hope that the author doesnt pull out a bullshit ''monster gets sudden power-up'' and all of those people die, especially after all the work that they've been seen to put into killing it.