This hotel actually has two separate loyalty programs: the Marriott Bonvoy program and, also being a Prince Hotel, the SEIBU PRINCE CLUB (SPC) for those living in Japan.
Those with the SPC second highest rank of Platinum are entited to breakfast in the restaurant, but do not get access to the club lounge(s).
Those with the SPC highest rank of Diamond do get access to both the club lounge(s) and the restaurant breakfast.
It's funny how the Marriott Platinum is the reverse of the SPC platinum.