Wait I’m so confused… I thought Glasses-Senpai was the same age as Mei Yuzu and Harumin/also in the student council… I also got the impression that Harumin and her sister had a bigger age gap like 5+ years……. did I miss something or did Citrus+ retcon that/make a new plot hole?…
Because they use the honorific, "senpai," it's safe to assume that she is older than Mei, Yuzu, and Harumin, but younger than Micchan. The time line works out well if Harumin and Micchan are 4 years apart. That means that when she was a senior, MYH(Mei, Yuzu and Harumin) were 8th graders. Which makes me believe that Glasses is 2 years younger than Micchan, so Glasses would be a sophomore. Meaning that the gap between Micchan and MYH is 2 years. So let's draw this out with words:
Micchan is a senior, Glasses is a sophomore, MYH are 8th graders (next school year) Micchan graduates, Glasses is junior, MYH are freshmen [they have now entered high-school] and then (proceeding to the next school year) Glasses is senior, MYH are sophomores (next year) Glasses has graduated, MYH are juniors and things are lined up to the time period of Cirtus now, I think. Of course, I did this based on the U.S. school system, so if MYH are actually seniors and not juniors; my math still works, you can just shift my calculations from taking away 1 year from my initial calculated guess.
And just for fun: MYH are 17 years old, Micchan is 21, and Glasses is 19.