Servers can add their own custom emoji including animations.
As you're on the same server as the original poster, you have access to the same custom emoji.
You can see all your server's custom emoji by pressing the emoji button (either ? or ? depending on if you're on app or website).
GNU social JP is a social network, courtesy of GNU social JP管理人. It runs on GNU social, version 2.0.2-dev, available under the GNU Affero General Public License.
All GNU social JP content and data are available under the Creative Commons Attribution 3.0 license.