FamousPrincess Mononoke1997 · Joe Hisaishi
Bar 5 of the song's introduction; bar 6 repeats the shape a whole step higher as F♯maj7(13)
An E major seventh chord with an added thirteenth (E, B, C♯, D♯, G♯) that appears suddenly in bar 5 of the Princess Mononoke theme's intro, far from the song's home key of C minor. The next bar moves the same shape up a whole step to F♯. Its notes fall into two small stacks of fourths, which is why it sounds lush but weightless.
Also called Mononoke 13, EM7(13)
Not yet confirmed by a second source.
Sources: TakKa, 【コード分析】「もののけ姫」の前奏のコードは四度堆積和音？ (Takka note blog, 2021-04-17) · Hooktheory TheoryTab: Mononoke Hime · U-FRET chord chart: もののけ姫 / 米良美一