Talk:Supporting Characters/@comment-38.121.251.227-20190827035040/@comment-30992949-20190827090734

That's a spoiler. In Part 2 of the Main Story or what's assumed to be adapted into the anime as Season 2.

In like, chapter 13 or somewhere around there (my memory of Part 2 is dying on me, I haven't read it in like a year...) we learn that Aya has been adopted by Takamasa Kujo- the guy who took Tenn away from the Nanases- after her original adopted family's company got bankrupted and disappeared. Apparently Takamasa saved that family's debt in return for taking Aya. Yotsuba is her original family name, but she became a Kujo after being adopted by Takamasa. She also became Tenn's younger sister after becoming a Kujo. Takamasa is a weird guy, adopting children from families that are in debt thus tearing apart said family and making said children into Top Star Idols™, but a great antagonist, but I digress.

I hoped that somehow answered your question and made enough sense.