What does "mint relationship" mean?

Mint Relationship tells the love story of a pair of twins Maria and Novi. Maria and Novi are the most suitable partners. They are the same person, doing bad things together, playing practical jokes together and even enjoying love together.

My sister Maria fell in love with the coach of Morimiya Academy Basketball Club at first sight. In order to chase him, she transferred to Morimiya in the residential system, and her younger brother Novi had to go with her sister. However, there are only girls' dormitories in Kesen Palace, and Novi's idea of dressing up as a man succeeded, resulting in some uncontrollable situations. A congenial boy, Takashi Sasaki, fell in love with Novi, and Novi fell in love with a roommate, Kimura, and her sister's love didn't make any progress. They are all caught in a complicated mint relationship. ......