There is an update to fix the "other" gallery related achievements. The issue only happened for people who has completed the game with the previous version, because the achievement would only been granted to people who hasn't unlocked the bonus cg. The new fix made the achievement available for people who has completed the game with the previous version as well. To get the achievement, you need go to the main menu after unlocking the bonus cg at the gallery menu. --- 「その他」スチルに関する実績の修正 実績を導入するまえのバージョンですでに全てのスチルをコンプリートしたら、「その他」のスチル全てを獲得した実績を解除できなくなる不具合を修正しました。 「その他」のスチルを全て獲得した実績と「全スチル獲得」の実績を獲得するには「その他」ギャラリーを確認後タイトル画面に戻ってください。

There is an update to fix the "other" gallery related achievements. The issue only happened for people who has completed the game with the previous version, because the achievement would only been granted to people who hasn't unlocked the bonus cg. The new fix made the achievement available for people who has completed the game with the previous version as well. To get the achievement, you need go to the main menu after unlocking the bonus cg at the gallery menu. ---