To reduce a buddy's load for setting its own presence information to associate presence information of a plurality of buddies with each other.

A buddy A designates a buddy B as a transfer source (#1). When the presence of the buddy B is updated (#2), the presence management part 10a of the buddy A determines whether the presence information of the buddy A is changed or not (#4). Namely, it determines whether the buddy B is the transfer source of the buddy A or not, and whether the latest presence information of the buddy A may be changed to the presence information of the buddy B or not based on a change rule or the like. When it is changeable, the presence information of the buddy A is rewritten by the presence information of the buddy B (#5). It is delivered to the presence management part of another buddy (#6). The latest presence information of the buddy B is reported to the buddy A.

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