I like how supportive/enthusiastic Madoka and Sayaka are about Mami's date. If we're assuming this is connected with this author's other works, then Sayaka's already dating Kyouko, so she isn't just being supportive because she wants Kyousuke for herself - she's just genuinely happy for them.
I just checked the artist's Twitter and this seems to be part of a series, maybe a doujin manga. It's actually pretty angsty, sexy but angsty, like Asuka and Tomoko are having trouble working things out.
^ same- Im gonna replay it soon too. I don't recall the teachers age - the age gap is probably about 10 years- Kiri is a 2nd year so like 16-17 - so mid 20s is gonna be 7-10 years- so its not THAT big a gap yeah.. assuming she is that age- she might be late 20s tho- it could be up to 13-14ish yr I guess.