So because there's no legal nor illegal translation of the prequel of this series (at least that I know of), I bought it in japanese from one of the official sites (Buyee). I don't understand the language, so I don't know exactly what's going on but it's clear by the art that the reason this girl (the student) is obsessed with the housewife is because she's the only one who cared for her when she was SA'd as a child (the housewide used to work as a nurse in her elementary school but she suddenly quit and that was a big blow for the protagonist). Because of this she develops a crush on this woman, which ends up as an obsession. It's actually pretty sad and it's the reason why this girl is the way she is is bcos it's a defense mechanism she picked up due to being afraid of being hurt once again. I wish I knew japanase so I could know the specifics.
Español:
Como no encontre traduccion legal ni illegal en ingles o español de la precuela de estos oneshots, termine investigando si lo podia comprar legal, y si, lo compre en Buyee. Como no entiendo japones, solo me estoy basando en al arte, pero basicamente la protaginista esta obsesionada con la ama de casa por que fue la unica q la esucho despues de q la asaltaran fisicamente (v**lac**n). La ama solia trabajar como enfermera en la escuela primaria de la prota pero termino dejando el trabajo y esto le cayo muy mal emocionalmente a la niña, asi q termina desarrollando como un tipo crush hacia ella q (basado en estos oneshots) termino como una obsesion. La verdad esta muy triste la historia y la unica razon por la q es como es es el resultado de no querer ser dañada otra vez.