It's not too often that an anime drops a surprise ending for its viewers, especially if it's within the confines of a story with an ordinary premise. Given the nature of anime as primarily an entertainment medium, viewers often expect an optimistic ending with the occasional villain redemption, mentor death, and heroic sacrifices. Even somber stories have expectedly grim endings, leaving a certain level of predictability to a story with their general themes. As such, when an anime pulls off an ending out of nowhere, it tends to leave a mark on a viewer's experience.