?????????? where is this heading
SPOILERS AHEAD!!
basically, the new book lover is Ilay's brother and the muscular hat dude is Taeui. Ilay's brother was commanded by Ilay to find Taeui, but despite Ilay being right infront of the brother, he has no idea since Taeui is living under a new identity. And then after a bit of drama, the gun lover teammate rats on Taeui and exposes his location which leads Ilay to find him. Then more r*pe, more angst, more "oh-look-I-dont-know-what-this-feeling-is from Ilay until they get together.
As for Taeui's twin brother, he is confined by some Arab dude (who becomes Jaeui's lover) to create weapons.
I hope my English was clear enough to understand. Have a nice day. ヾ(❀╹◡╹)ノ~