I’m not entirely sure what the intended audience for Genocider Mode is supposed to be. You see, it’s not for people who haven’t played the game, because it absolutely speedruns the story to the point of removing most of the depth (it’s approximately 16 hours of dialogue-driven game crammed into two volumes for fuck’s sake). But it is also not exactly for the people who have played the game or are even fans of it, exactly because it’s just a really short summary leaving out a lot of stuff (and even modifying some so it could cram in more of the plot in shorter amount
Well, the idea behind this is supposed to be the story but told from the POV of Toko Fukawa. That is a cool idea at all but I feel the one who pitched such idea kinda forgot that she the other half of the protagonist duo, meaning that her POV is going to be the same as original narration almost all the time. This ends up with a short part at the start and another part in the latter half of the 2nd volume that are narration unique to this manga. So the rest of this just ends up feeling as a rushed filler to connect those two points and I feel this would work much better as a longer one-shot with just those unique points. There really is no need to summarize the main story, especially as it already has another manga that covers it.
I can’t fully judge the characters of this as I’m already familiar with them from playing the game, but I imagine they feel much less interesting with the little info about them this manga offers, so again, you’re supposed to be already familiar with the source material I guess. In which those characters are interesting.
Overall, this is just if you’re both Danganronpa fan and a completionist. Alternatively if you’re interested only in the extra content you can just read that and skim through rest of the manga, you’re not really missing out on anything else.