From The Heretic Knowledge Vault
| Chapter 28|
05/23, 05/25, 05/28
A school chum of Meji's. She tries to cheer Meji up after her return to Tsuiraku, but with no success. She then tries to talk sense to her and get her to take responsibility for her own actions. That doesn't even work as well as the attempt to cheer her up, unsurprisingly.
From this thread
If memory serves, she only ever appeared in a picture frame in a old non-story piece of artwork, and the closest [that] she came to being mentioned in the actual story was that statment from her grandfather.
Basicly the idea was while Bani was the friend closest to her actual age, Etsuko was the friend closest to her apparent age.
And while Meji has actually known her longer than Bani, they're not as close as they used to be due to the fact that they didn't get to see much of each other for a few years since Etsuko only recently became old enough to go to Meji's school.