Birthday Song

Birthday Song is the twentieth episode of the Log Horizon 2 anime and the sixth episode of the Route 43 arc.

Synopsis
Nyanta lands on Plant Hywaden's train and immediately clashes with Londark. He learns that Plant Hywaden intends to trigger the war with the People of the Earth, which Shiroe had once proposed as a possibility. Nyanta tries to reason with Londark, who is angry and hates the fact that he was forced to come to this world. Nyanta resonates with his understandable hatred towards having no control in his new reality. However, Mizufa Trude silences Londark by throwing him off the train and into a grinder out of pure boredom, and proceeds to clash with a now-enraged Nyanta. Mizufa reveals her desire for war and bloodshed, and refers to the adventurers as "undead". Nyanta goes in for the killing blow, but is stopped by Kazuhiko.

Meanwhile, Plant Hywaden's puppet guildmaster, Nureha, strolls casually through the streets, dropping her disguise as she reflects on her recent journey with the children of Log Horizon, particularly Touya and his last words to her. Roreil Dawn finds her, and she orders him to slay as many of the attacking wyverns and nightshade servants as possible, much to his surprise. She then dons her disguise again, and leaves.

Back on the train, Nyanta reflects how Shiroe had asked Kazuhiko to change Plant Hywaden from the inside, but in Nyanta's eyes, Plant Hywaden had changed him instead. Kazuhiko informs Mizufa that the mission has been cancelled by Nureha herself, and tells her to withdraw. Nyanta, still angry at Mizufa, tries to kill her, but Kazuhiko stops him again, knocks him down, and cuts off the train car Nyanta is on, because he didn't want to stain Nyanta's hands with the blood of a Earthling.

Back in the town, Rundelhaus Code and Isuzu continue their battle, though Isuzu realizes there is nothing she can do to protect everyone. At that moment, Roe2 arrives, and provides backup with the help of her summon, Sword Princess Al Quenje. Isuzu decides to sing, vowing to love music from then on, and reflecting on the similarities to her plight, and Rudy's desire to become an adventurer. Serara meets up with them, and via telepathy they hear Toyha, still trying to stop the Odyssey Knights. Upon arriving, and remembering the events of that day, Isuzu, becomes angry, and starts to play her "43rd Song", the first song she ever wrote herself in Elder Tale.

Trivia

 * In the light novel, Mizufa actually runs Londark through with her sword before throwing him off to his death.
 * The lyrics to the 43rd Song were written by Mamare Touno himself.