This was one of the last stops our tour group made when I took a brief trip several years ago. I only made it up a fraction of the way myself, but that was partly because we were only there for a few hours. (Comparing with the map here and judging from the branching paths I recall seeing at highest point I reached, I think I got as far up as Mizuki-san did.) Getting all the way to the top might have been possible if it was an all-day thing...and if I were in better shape.
Reader-added tags include "Death Mountain", "give_up" (like that, in English), and "There's no response. It's just an umbrella" (riffing the stock phrase from Dragon Quest).
Oh, god, I remember when I went there last year, and I stayed at the cheapest inn I could find so I could save money for going to comiket next week. I walked all over Kyoto and had a lot of fun.
I only made it about there as well, because I went off on a smaller road and ended up somewhere in the mountains, before I had to turn back because it was dusk.
I remember feeling like that when I made it to that same sign. Was on crutches because I broke my ankle but we were lucky that no one was around because it was so early. Could take my time getting to the top.