Finished watching episodes 7–10 of
Monogatari Series: Second Season, which covers the
Mayoi Jiangshi arc.
The premise of the arc starts pretty simple. We all remember from Bakemonogatari that Mayoi Hachikuji ran away on Mother's Day so she could visit her mother. But never got there because she got ran over by a car and died. Currently, she is a ghost in the present. What if Koyomi saved her? Given that possibility right in front of him since Shinobu failed to time travel them in the time he originally wanted.
However, things like this aren't as simple as we see here. As both Shinobu and Koyomi return t
We actually get a strong answer to why the world was annihilated. Essentially, back in Bakemonogatari when Shinobu ran away we do learn that she wanted to destroy the world. As expected from the events of Kizumonogatari, Shinobu in some ways was miserable. She wanted to die and Koyomi did not let her do just that. We also learn that Shinobu was in a much childlike state of mind. After all, she wanted to have that purpose for living.
Now originally she finally realized that reason for Koyomi, but no surprising a vampire that lived alone all of these years, would have trouble figuring that out. Koyomi finding her in Bakemonogatari is what triggered. The issue here is that Mayoi is no longer an apparition or ghost. And it is because Mayoi exists as that is how Koyomi was able to find Shinobu. With that happening, he dies to Black Hanekawa, which triggers Shinobu to fulfill her childlike manners in destroying the world.
However, despite the world being annihilated, Koyomi finds a grown up Hachikuji. A very bittersweet moment for Koyomi as despite saving her caused all of this change, the fact she is still living is a happy moment for him. Hachikuji gives Koyomi a note from Oshino. With a giant reveal that you can't change destiny with time travel. More than like what it means is, you can't change your destiny. In this route x, which Koyomi saves Hachikuji, this was a route in which Hachikuji lives. Koyomi going back in time is how Hachikuji gets saved in this route x.
Oshino also asks Koyomi to save this route of the world. Koyomi has always been a guy who put others over himself time and time again. After seeing Hachikuji all grown up and the thought of her living in this awful world is sickening. After all, he wanted to let Hachikuji live a life she should have had. Despite the cruel reality this is a Hachikuji that never knew Koyomi and this is a different one then in his route. Still knowing that some version of her can have the life she should have had is good enough for her.
Now, to save the world, they would have to face this version of Shinobu. Well, she is retaining her Heart-Under-Blade form. This is a great scene showing how just a little difference can make. For Heart-Under-Blade realizing that was Shinobu and Koyomi from another route. Realizing the happiness that she could have had. While for Shinobu while she understands why Heart-Under-Blade annihilated the world. To think that saving Hachikuji could change history so much. It really signifies the idea of regret and changing something can have a much bigger impact then you would think.
Despite Shinobu being so blunt, Heart-Under-Blade seeing Koymoi and Shinobu together made her happy. Oshino's point of dealing with Heart-Under-Blade was to show what could have been. It lit a fire under her in realizing the mistake she made. Much like Koyomi wanted Hachikuji to live the life she could have had. Heart-Under-Blade wanted Koyomi to continue living the life he had. Sacrificing herself, so those two can go back to their route.
At the end of the day, nothing changed in this route a for Koyomi. As Hachikuji is still a ghost, but her remark about being able to meet Koyomi meant a lot to her. Sure, her life could have been so different, but she doesn't regret what happened. The key message being that while not everything goes the way you want it, but it is better to look at the good rather than the bad. Fantastic arc that holds up for the first arc surrounding Hanekawa in this second season.
