Links
I'm leaving in a lot of my Himeji links here; they're needed if you want to visit Seppiko. I've also included some Seppiko-specific links.
Seppiko Links
Himeji Links
Hyperdia (train schedules)
metroPlanet - Asia - Japan - Osaka Subway
Seppiko is a mountain northwest of downtown Himeji. How long it takes to get there largely depends on how you go. It is technically possible to get there using public transportation, and certainly if you want you can ride a bicycle there; it's not a bad ride, though I've only personally ridden about halfway to the mountain (I wasn't on a road bike, but a mama chari, the type most common for commuters going to/from their homes and the train station).
From a distance Seppiko is impressive. It's not a large rock formation, and while it has some challenging routes they're hardly 'world class'. But it is still a very nice climbing area. It's also good for hikers, particularly if you like to scramble a bit.