Kohina's past life (in anime)

One scene in the manga suggests that Kohina comes from a violent household with it's members often fighting, forcing Kohina to shut her ears and become the emotionally-unattached "doll" that she claims to be.

Kohina's Past Life

Kohina's Past Life

Kohina actually met Kokkuri-san in her past life. However, she did not have any recollection of this. Today, Kokkuri-san haunts her only to fulfill the promise he made with Kohina's past self which was to make her smile everyday.