As the story progresses, the mangaka gradually reveals information about what is going on, which is no easy thing in a one-shot. No big deus ex machina info dumps here. Everything makes perfect sense.
The characters are appealing and their personalities suit who they are. There is one crazy, slapstick incident that makes no sense, but it does break up the drama nicely.
Add in a great tear-jerker ending and you have an excellent product.
The only problem here is the MAL software insisting on longer reviews. It's not exactly easy to do that when you're talking about a one-shot.
