Surprisingly enough…! 
Yes, all the time I’ve been in Japan I’ve worked in Ikebukuro, and for 99% of the time I’ve lived on the Seibu Ikebukuro Line. However, as for ticket prices…
… until this work-from-home period, my company always gave me the money to get a commuter pass from my home station to Ikebukuro, so I never gave it a second thought. Commuter passes are great because you can actually get on and off at any station within the commute, and use it on days you are not working too.
All that has gone now, sadly, and on the very rare occasion that I do use a train (perhaps 4 times in the past 4 months), I do the same as you and just use my Pasmo. In fact, thinking about it, I don’t think I’ve ever used a paper ticket in Tokyo.
Anyway, looking at their ticket, my Japanese isn’t good enough! I’ll ask the expert when I see her tonight.
However, what I don’t understand is why they are starting their journey on the Seibu Line at all (even given that 紫陽花 may not be a real place). They live in Kansai, right? How did they end up somewhere along the Seibu Line? (Unless they arrived by rocket, as per page 118).
However, after that, the pages are wonderful! Every working day of my life for almost a decade I have seen the same view that Yotsuba sees on page 126 as she pulls into the station, and the route from the Seibu Line to the Yamanote is also very, very familiar to me!
In many ways this is the volume I’m most looking forward to reading, just for all these pictures of places I know so well. I’ve lived in Tokyo longer than I’ve lived anywhere else in my life and know this city better than anywhere else (especially after being a tour guide here as well), so looking at these drawings is wonderful.
But also sad. Look at the glorious station on page 141, which is being torn down as even as we speak. (The replacement station has been built a couple of hundred yards up the road. But instead of preserving this one, they are demolishing it).
The thing with the strawberry on top looked so good…churros seems like a random thing for a fancy buffet to have, but I wouldn’t complain.
Giving off those “this could be a series ending” vibes again (but Wikipedia tells me there are already more chapters not yet compiled, so surely there will be another volume eventually!)