is jujutsu kaisen episode 13 filler?

Yuji and Nanami launch a coordinated assault against Mahito. They gain the upper hand through teamwork — Nanami's precision creates openings that Yuji's soul-damaging punches exploit.

Cornered, Mahito deploys Domain Expansion for the first time, trapping Nanami inside Self-Embodiment of Perfection. Yuji breaks into the domain from outside, disrupting Mahito's concentration and saving Nanami.

Mahito escapes, but both sides now understand each other: Yuji is the one thing Mahito's technique can't easily handle.