Just got back from my stay as a diamond. No upgrade was offered but hotel was full so I didn't ask further.

Breakfast is a set menu (you get yougurt, fruit, salad, unlimited drinks, and pick a main). All were good.

Staff were super friendly, almost too much, but it's Japan so you just gotta go with it.

Room wasn't ready when I got there at 11:30/12. They held my bags and I returned before dinner. Check out is noon but they extended it until 1 without hesitation when I requested it. Large table and chair in the middle of the room took up a lot of space unnecessarily but that was my only slight complaint.

Room was a good size and faced the river so great views. As stated, you can take any food from the minibar for free (but they're not restocked). Drinks are chargeable. Hotel was immaculately clean.