I'm not going to bother quoting all the things in this thread I wanted to since many say similar things. I think I opened at least 5 tabs worth I wanted to comment on. Instead I'll just drop some knowledge.
In the USA, I'd say the first exposure to this sport is some form of a climbing wall in school, most likely with a rope or automatic belay system that one can hook into without a second person with a rope. That is NOT bouldering. Bouldering is climbing on a wall maybe 15-20 feet in height (indoors there are usually padded mats, outdoor they use movable drop mats). I would say with the upcoming Olympics that Sport Climbing is gaining a lot of traction in Japan seeing as they seem to have a pretty strong team.
I have been regularly going to an indoor climbing gym and I almost never use the ropes, or the auto belay system - it is a different area of the gym entirely! This is more due to not having a regular partner to climb with (and not caring to join strangers lol). Bouldering is a nice gateway to the sport if you are OK with taking some falls and learning your limits. I am also very scared of heights! Bouldering has helped immensely with this fear.
The only real trigger for me in this thread was
Wall climbing is just simply not something that can keep you engaged for long. After a year pretty much everyone can climb most courses. It's not even something most people would consider a hobby (unless you combine it with parkouring). If this is entirely about the yuri, then the wall-climbing should not be the central premise or the titular focus!
This is entirely bullshit on both the climbing point and the yuri point.
1) If climbing/bouldering were that easy, where is the skill involved? Did you know that for some of the finger training, there is a MINIMUM requirement of a couple of years to even focus that kind of training, lest you bruise/blow out tendons in your fingers? No, you wouldn't. This is TMI for the whole thread really, but as an athlete I've learned to not be dismissive of almost any sport.
2) Climbing is part of the plot of getting them to have an interest. If you want another generic love story, go look for not a sport yuri lol. These series are fun usually because they integrate real techniques and skills. Oftentimes, they go a little out of this world (first thing that comes to mind is something like Prince of Tennis), but it's FICTION and it's fun.
...I personally like this genre to be more realistic, though.
Lastly, let me initiate everyone into some easy watching! Over the past year or so I've been watching IFSC Lead and Bouldering competitions. Why? Because the ladies are strong and HOT! LOL. Real talk, they have muscle, the moves are so, so strong and difficult to execute, and the sport is dynamic and fun to watch at times. Ages range from maybe 15-30ish.
https://www.youtube.com/watch?v=1mloFMXs-Yk
Link to IFSC World Championships in Hachioji, Womens and Mens bouldering