You Are Seriously Addicted to Acting.

Why Koreans care

The “Nico Nico Nii” routine is Yazawa Nico’s signature introduction, not a new LE SSERAFIM chant. The captions stress fidelity to the original, and the members even use a piano to set the opening syllable at F-sharp—a rehearsal detail worth listening for when the routine finally appears onstage.

In the Korean comments

One comment pinpoints Chaewon’s “seductive” version at 0:50. Another says they have never attended the group’s concert but, after hearing friends call it extraordinarily fun, this backstage video helps them imagine what those friends meant.

What the words mean

“당신은 심각한 연기 중독입니다” (“You have a serious acting addiction”) sounds like a formal diagnosis, but it is a mock-serious caption for how the emotion game becomes difficult to stop: the members keep requesting new versions and new lines. A commenter echoes the joke with “난 심각한 르세라핌 중독” (“I have a serious LE SSERAFIM addiction”), an affectionate, exaggerated way to say they cannot get enough of the group.