https://www.animenewsnetwork.com/news/2019-04-06/high-rise-invasion-manga-gets-sequel/.145446
The sequel will be published here: https://pocket.shonenmagazine.com/
Obviously no official English version. So I hope some scanlation group gets this manga as a future project.
Yea I agree I'm a fan of thriller manga and that's how this began but it turned into a battle manga that kept getting dragged out. I finished the manga and the end is way too sudden (btw it ends as a 2 part so 257/258) the only reason I kept reading was because of Sniper Mask.