近所のやさしいおねえさん The_Nice_Neighborhood_Lady
Every day after leaving elementary school, Otone-chan visits the kind lady living near her home, since she can't play outside with her school friends due to her frail body. The two have a secret, though: They're lovers.

[spoilers]The story contains heavy "yandere" undertones, with implications and hints that Otone-chan's lover is a yandere, or has other attachment issues that could be violent in nature.[/spoilers]

Manga by [[Itou Hachi]].
kinjo no yasashii onee-san