Ibuki was most likely neglected as a child. Why do I say this? Well, as the past chapters state she puts her loudness on speaker so she can get attention, tho, this loudness on speaker thing in probably unintentional as she tires herself out quickly with.

And along with the fact she has amazing emotional intelligence. Is it just me or do neglected kids just sense everyone's shit? Like, since they're either being neglected or vented to by their parents, they just can sense everyone's shit. And Ibuki could easily tell what was wrong with Hajime, and most likely everyone else on the island. Causing her to basically bleed herself dry to help all of them. Wether that be putting on a show or giving a free therapy session.

Also, the only thing truly personal she states about herself is that she's often so lonely. Neglected kids usually are, causing them to create their own little world in there head and to dive deep into different form of creativity. Such as sewing, music, fashion, ect.

And to add the little cherry on top, Ibuki is cannonly 5'4 and 96 pounds. Extremely frail for an 18 year old. That leaves me to believe three options for why this is. 1. She usually doesn't get food at home. 2. She has an ED. And 3. The music company she worked with when she was in her girl group starved her and her band mates to keep them looking "beautiful" to the public eye.