This "last" volume serves as an epilogue for most of the major characters in the series.
We finally see what happened with Akimura (Tsukasa's friend from the very beginning of the series) after he was arrested. I was always hoping for some sort of follow-up there, and I'm glad we at least got to see how he ended up.
Ushio sucks, so I didn't really care about his ability to "find his freedom" or whatever the hell.
Kikuhara also sucks. But Nine and Seven at least get some closure in regards to how they view him, and whether they'll be "family" someday.
Lee was done the most dirty in this series, and considering he's one of my favorite characters, it really sucks. He was just sort of tossed to the wayside in the last few volumes. During the first time-skip, when everyone was split up and investigating in their own way, Lee is just...left to his own devices, wandering around, seeing Feng sometimes, being hunted down. Then he gets wrapped up with Queen, which wasn't a bad thing in the end, but Queen told him how important his role was and then he just gets a few scenes for the live stream and is tossed aside again. Tsukasa had tried to get in touch a few times, but he was part of the fam and like no one else gave him a second thought or worried about him. Then, he gets this little story where he's still off wandering, befriends a little girl and her grandma, and then has to run off again. I get that his "freedom" was an important aspect to his character, but he was also happy to be with Tsukasa, Yuki and co. It just really sucks.
And then we have our precious couple, meeting Tsukasa's parents and grandma, and working out the worries of all involved. It was a really sweet wrap to their story arc. The extra bonus story about Sawazaki and Jill--and also Tsukasa and Yuuki--was sweet, but honestly I was hoping to see more exploration of the physical side of the main couple's relationship.
I think this series will likely stick with me for a while. Gonna watch the anime soon.
So long for now, Devils' Line.
(Plus, there's an ongoing sequel currently. I don't know anything about it, but I'll keep an eye on it.)