Wow! that ending sucked ass!
Volume two was doing the whole "our comic isn't popular enough so lets introduce a new character to add conflict" thing which is a bad start, and the tone switch to being more dramatic than comedic was kind of sudden, but there were some parts there that I liked (though the random ecchi shots felt more out of place). I thought it was nice how they created a foil for our main character to show how she's a "good" yandere when compared to a "bad" yandere because she genuinely wanted her crush to be happy and she never crossed the line from creepy stalker to attempted murderer. And they even had the parents as model for what accepting a yandere might look like. I thought the ending was going to be something like Mero and Edogawa helping Sazi to express her love in an acceptable (if over-enthusiastic) way, thus surpassing her mom by actually having a loving relationship with the girl she's obsessed with. They really put a lot of leg work into making a happy ending make sense (which fits tonally with the first volume being a comedy).
But then she just kills herself? Genuinely feels like a troll ending. She talks about her sins, but her crimes were all downplayed by the narrative, and the worst thing she did was the kidnapping, where she just immediately let Edogawa leave. If they were going to have her kill herself, shouldn't the second volume have shown some actual build up to that? Like we see the consequences of her crimes, or we see how she gradually becomes more unhinged, rather than the exact opposite of that, which is what we got. And if they wanted to do a shocking twist where she dies, they should have had at least a chapter or two of aftermath, like showing the other characters reactions to her death. As it is, it's just a single non-sequitur scene with no set up and no aftermath, that can only make you feel baffled and frustrated. Zero pathos.
Based on the early chapters, I thought the second volume would be something like Sazi tries to get closer to her crush through more legitimate means, like going on dates and stuff, while Mero tries to help her, but she's awkward and having her emotions stirred up causes her to do more crazy yandere shit. And then Mero starts to crush on Sazi as hinted at a couple times in volume 1, resulting in a very silly love triangle. Then volume 3 would be the last one and would have a somewhat more dramatic tone with the love triangle getting resolved in some kind of happy end. No interloper character. I think this would have been much better and would have matched the tone of volume 1 (which was good).