Happy Sumo Japanese Restaurant

The Happy Sumo was a nice place to eat. I went with a friend on a Wednesday night so business was kind of slow. The waitress was very attentive and the atmosphere was relaxing. The only problem I had was when it was time to leave. My bill was only $40.00, I left the $45.00 on the table. As I was getting ready to leave the waitress chases me down asking me was I not happy with the service. At first I did not know what she was talking about. She was like you only left 5 dollars and I was like what is the problem. She said I did not tip her enough and I was suppose to tip her 18%. i kindly told her she was not going to be given anymore money and thank you for the good meal!!. This has never happened to me before so i am not sure i will be going back to this place. This was a very odd experience.