The Misfit of Demon King Academy Episode 4

15th Birthday (十五の誕生日, Jūgo no tanjōbi) is the 4th episode of Maō Gakuin no Futekigōsha anime series.

Synopsis
Misha confesses the shocking truth that, “At midnight on my 15th birthday…I’m going to disappear…” Misha was never supposed to exist in this world in the first place, but due to Ivis Necron’s magic, she was living a transient life. She had resigned to her fate that she will only live for 15 years, but Anos tells her, “There are two things that I do not understand. Regret and saying that something is impossible.” The misfit crushes the tragedy and unjust fate that binds the two sisters.

Characters
In order of appearance:

Summary
When Sasha was a fetus, Ivis split her into two babies so when they turn 15, they would fuse into a single more powerful demon. Anos catches up with Sasha who reveals she actually wants to save Misha, and she created a spell to let Misha live while she disappears. Misha refuses so they tearfully wait for Misha to disappear. Anos reveals that if he sends them back in time, they can fuse with their unborn fetuses, so they will be born as true twin sisters. Anos is then stabbed by Ivis, who plans to use their fused body to host the true reincarnated Demon King. Anos activates  only to be blocked by Eugo La Raviaz, the Guardian God of Time. Fusing himself with Ivis, he kills Anos and admits he altered history so no one would know Anos made a deal with Kanon to end the war. Anos reappears unharmed, revealing he has enough power to even defy a God. He sends Sasha and Misha to the past to fuse with their unborn selves. He then destroys Ivis. After resurrecting Ivis, Anos returns all his unaltered memories, revealing Ivis only betrayed him because his memories had been altered by someone working for Avos Dilhevia. Sasha and Misha return, now as true sisters with separated roots. Despite having saved Misha and altering the past, Anos nonchalantly decides to return his scepter to get a perfect score for the academy challenge.