見み mi 栄え e だよ！ da yo

Noun 🔑
Vanity, showing off, keeping up appearances. Refers to putting on a front to look impressive. Key expressions:
・見栄みえを張はる = to show off, to put on airs
・見栄みえっ張ぱり = a show-off, a vain person
Anon confesses that joining the band was never genuine — it was just to look cool.

Copula (Plain)
Plain form of です (desu) = "is/was." 見栄だ = "It's vanity." More blunt and direct than です. Anon drops all politeness here — this is a raw, honest confession.

Emphasis Particle
Adds assertion and emphasis. だよ = "It IS, I'm telling you!" The よ makes the statement forceful, conveying "listen to me" or "I'm laying it all out." Anon is confronting both herself and the others.

Extended Expression
In the same scene: 見栄で始めたくせに (You started it out of vanity, and yet...). で marks the reason/cause, くせに = "even though / despite that" (accusatory tone).