For those coming to Himeji by motorcycle, here is a guide to parking. 🙂
The only one motorcycle parking lot in the vicinity of Himeji Castle is…”the Otemae Park Underground Parking”.
It is 500 yen for a day (24 hours from entry). Here are the details (in Japanese only)
https://himeji-machishin.jp/toshi/parking/parking_1/3p-chika/
It is a 1-minute walk from the guesthouse. It is also close to the castle. Please use it.