There's one thing for sure that I can say without a doubt about this manga...
WHAT A WASTE OF POTENTIAL!!!
Now, for the longer version...
Killer Killer, this manga is the spin-off for the anime Danganronpa 3 The End of Kibougamine Gakuen that pretty popular at the time.
Now, for starter, our main character names Hijihara Takumi (that looks very similar to Hikigaya 8man from Oregairu) is a serial murderer that kill other serial murderer because they lack the passion of the killing itself.
There's also our other main character, which is a girl names Asano Misaki who is a newbie in the office.
Now, there's a lot of problem in
here, but I'll start with the investigations.
They just skip it with the words "I know passionate murders" and just skip to the finishing story. I mean, Danganronpa is indeed bizarre but it's still a mystery game with a fun investigations and figuring out who's the murderer is. But this manga feels like "Fuck all the investigations, let's get to the part he kills someone already!" in a very bad way
And than there's the story... now, the main ideas of the story is quite interesting, but there's just so many wasted potential in here. They just keep making more and more cameo from the Danganronpa 3 series that it becomes boring since they just show up in one moment and have almost no part or significant effect to the rest of the story, they're just.. there.
Some of the part where Killer Killer kill someone that is just way too OP for the Danganronpa universe. I mean, not even Kamukura Izuru can cut the whole roof of the building in one slash with a knife
Overall? I think they have to remade most of the story. The main plot about a murderer that kill other murderers not because of justice, but passion itself is a very interesting. But the minus points just keep covering the plus.
The cameo is nice, but please make them more meaningful rather than just about them showing up in one moment and disappear in the rest...