[Kyuusaisha]

Finally got around to starting this now that the anime started airing and I have a simple question.

Spoiler:

Since Mayumi & Mari are third years at the beginning of the story do they no longer appear after the 1st year for the siblings has passed? Since, I've pretty much been reading spoilers like a crazy person since getting into this I wouldn't mind being spoiled even more since I couldn't really find information regarding this. Thanks