So stupid ending. Ruined all of the impression for me. Looks like authon didn't even bother himself to think up at least something to end this manga, so he just "oh, she disappeared, I'll leave it to your imagination".
Bullshit.
I kind of agree with this, in that it's not especially great storytelling. On the other hand, it's very Japanese. They've got a pretty long history of ambiguous endings, especially in literature.
I like ambiguous endings. They can often be pretty fun to puzzle together. This one was just kind of flat though. I you're doing an ambiguous ending you should at least make it intriguing.
Ambiguity has a time and place, but as underachiever said this one lacked depth. It's totally fine and can often be insanely powerful to knock us out with a 1-2 punch that we totally weren't expecting, but there has to be at least some clue as to the 'why' otherwise you lose about 40% of your audience.
If there was a continuation, that'd be one thing. But if you force a car to stop without warning, you'll probably end up crashing it.