...this feels way too "fine" of an ending.
I understand the purpose of making it that simple, the climax is over and there's really not much to mull over now that she managed to tame him by giving him her affection, but I expected at least her taking more agency in the entire thing.
There were bits and pieces where she was actual character and not just the "stop onii-chan become a murderer" record player, but this ending where she just gets dragged along by him into a relationship after everything that happened feels...like they flattened her character way too much for the sake of a clean and easy resolution, more done for fanservice to the couple angle since there wasn't material to decently expand upon their change in dynamic now, than to actually explore what their relationship would be like now and how Mai's agency works with her brother.
Unless the point is that it now is severely restricted by her brother's fully unleashed obsession, in which case this is a way more depressing ending than one would initially think, and I don't really know how to feel about that.
Reading it again...i guess my issue really is that they don't show any new scenario, anything that would show what their relationship is, beyond those last 2-3 panels. It talks about things that happened to them to get them to their current point, but feels weird when they don't show how they live out a normal day in their life, how being a couple affects how they live now. Which is what I wanted out of this ending. Hopefully if it has an epilogue it shows that, because if not, it would feel a bit too...empty for me. IDK. Being up at 4 am and checking this excitedly, just to read something this plain from this series probably wasn't a good idea.