CORE is MERRY's official fan club, which offers privileges for an annual fee. Joining CORE requires an address in Japan. Some shopping services specialize in fan club memberships.

The list of CORE member privileges, as advertised on the CORE login/about page, is as follows:

The membership fee for CORE is a one-time admission fee of ¥1,000 + an annual fee of ¥5,000, i.e., ¥6,000 when you first join.