Artist's commentary
[Obaa-cha~n]
[Remilia Oba-san's here]
[Don't call me Oba-san, you middleschooler]
Even your old friend's grandchild is calling you Oba-san, Ogishi-san (elder sister-in-law).
By the way, it's OK if you imagine that this series is chronologically around the time this situation takes place.