diff --git a/data/src/main/java/one/nem/lacerta/data/LacertaLibrary.java b/data/src/main/java/one/nem/lacerta/data/LacertaLibrary.java
index eeb8546b..cb19b425 100644
--- a/data/src/main/java/one/nem/lacerta/data/LacertaLibrary.java
+++ b/data/src/main/java/one/nem/lacerta/data/LacertaLibrary.java
@@ -1,6 +1,7 @@
 package one.nem.lacerta.data;
 
 import java.util.ArrayList;
+import java.util.concurrent.CompletableFuture;
 
 import one.nem.lacerta.model.ListItem;
 import one.nem.lacerta.model.ListItemType;
@@ -11,15 +12,13 @@ import one.nem.lacerta.model.document.DocumentDetail;
 public interface LacertaLibrary {
 
     // Get History
-    ArrayList<ListItem> getRecentDocument(int limit);
-    ArrayList<ListItem> getRecentDocument(int limit, int offset);
+    CompletableFuture<ArrayList<ListItem>> getRecentDocument(int limit);
+    CompletableFuture<ArrayList<ListItem>> getRecentDocument(int limit, int offset);
 
     // Get Library page
-    LibraryItemPage getLibraryPage(int limit);
-    LibraryItemPage getLibraryPage(int limit, int offset);
-    LibraryItemPage getLibraryPage(String pageId, int limit);
-    LibraryItemPage getLibraryPage(String pageId, int limit, int offset);
+    CompletableFuture<LibraryItemPage> getLibraryPage(int limit);
+    CompletableFuture<LibraryItemPage> getLibraryPage(int limit, int offset);
+    CompletableFuture<LibraryItemPage> getLibraryPage(String pageId, int limit);
+    CompletableFuture<LibraryItemPage> getLibraryPage(String pageId, int limit, int offset);
 
-    // GetDocument
-    DocumentDetail getDocumentDetailById(String id); // TODO-rca: Documentに統合する
 }