is jujutsu kaisen episode 51 filler?

Mai Zenin sacrifices her life. Returning home for cursed tools, Maki confronts the Zenin clan.

Ogi tries to burn his daughters alive. Mai uses Construction — the ability to create one real object at the cost of all her cursed energy — to forge a sword for Maki.

She dies in her sister's arms. The twin bond shatters, and Maki's Heavenly Restriction activates in full.

Her body perfects itself into something comparable to Toji. She takes Mai's sword and destroys the clan that abused them both.