Shinobu opens by describing what Tsukihi is – a “Dying Bird” – like a phoenix, but more like a cuckoo that lays its eggs in the nests of other birds. Thus Tsukihi is fake and immortal, but ultimately harmless. After leaving Karen to guard Tsukihi, Koyomi and Shinobu go to the cram school to confront Yozuru and Yotsugi, respectively. After much discussion, Yozuru brutally beats Koyomi, but he doesn’t die. Shinobu handily defeats Yotsugi, and a heartfelt declaration of commitment from Koyomi makes Yozuru philosophically conflicted, such that she retreats, content to let Tsukihi live with Koyomi as her mentor. Life returns to normal for the Araragi siblings, and Koyomi promises he’ll let his sisters meet his girlfriend.
One thing we’ve learned from watching several of Akiyuki Shinbo’s works: he doesn’t skimp on endings. He didn’t skimp here. This was an impressive finale, blending bold, fast-paced, dramatic animation and music with lots of smart and intriguing philosophy (Yozuru even breaks out Mencius and Xun Zi), and wrapping up the story nicely by getting to the root of things. Shinobu drinks some Koyomi blood and powers up to her adult size, which is a dead giveaway she means business (Her exchange of taunts with Yotsugi prior to their duel is priceless). Finally, Yozuru proves to be far more flexible than she originally seemed. Rather than having to kill or defeat anyone, Koyomi gets off with a severe beating (he quickly heals from) and a goodbye.
We were expecting a nonfatal outcome, though. Koyomi’s dealings with Oshino and Kaiki, combined with the resolve bourne from his unconditional love of his sisters, lend him the strength to stand up to Yozuru’s verbal sparring and come out the victor, making her forfeit. It’s not surprising she was university buds with Oshino and Kaiki, and it’s neat how the three of them have totally different beliefs when it comes to the value of real versus fake – crucial in the climax. Yozuru believes the real is worth far more. Oshino believes they’re equal. Kaiki believes the fake is worth far more. It really sums up their respective M.O.s. Koyomi seems closest to Oshino on this point: his sister may be a fake, but she has always been his sister and he has always loved her, so it makes no difference to him.