According to the tags on pixiv, the three other ladies are Kawasumi_Mai's mother, Misaka_Shiori's (and Kaori's) mother and Tohno_Minagi's mother. I don't think they have real names so I didn't tag them but feel free to fix that.

So... it's the neighbourhood milf sports meet?

What does milf mean?

Mother I'd Like to Fuck

NinthAltima said:
What does milf mean?

You, my friend, just failed in so many ways.

Hmmm. Shiori and Kaori mama?

Never saw them as far as I remember...

wtfbagels said:
Hmmm. Shiori and Kaori mama?

Never saw them as far as I remember...

In the 2006 Kanon anime series, she appears very briefly in the first episode, and then again in ep. 16.

Aunty Valleyball Society

The mature pheromones must be thick in the air.

Shiori and Kaori's mother was seen and heard in the 2006 anime but she never made any sort of appearance in the original visual novel...

... So it all depends on what you believe is "canon"

Sorry, I had to do it.