diff --git a/include/core.h b/include/core.h
index 71e99d2..e12c938 100644
--- a/include/core.h
+++ b/include/core.h
@@ -86,9 +86,6 @@ int sasahyou_init(Sasahyou *sasahyou);
 // Free sasahyou
 int sasahyou_free(Sasahyou *sasahyou);
 
-// Weed sasahyou
-int sasahyou_weed(Sasahyou *sasahyou);
-
 // Load sasahyou from file
 int sasahyou_load(Sasahyou *sasahyou);
 
@@ -118,9 +115,6 @@ int sappyou_init(Sappyou *sappyou);
 // Free sappyou
 int sappyou_free(Sappyou *sappyou);
 
-// Weed sappyou
-int sappyou_weed(Sappyou *sappyou);
-
 // Load sappyou from file
 int sappyou_load(Sappyou *sappyou);
 
diff --git a/src/core/sappyou.c b/src/core/sappyou.c
index f1d8b60..0b49e24 100644
--- a/src/core/sappyou.c
+++ b/src/core/sappyou.c
@@ -28,24 +28,6 @@ int sappyou_free(Sappyou *sappyou) {
     return 0;
 }
 
-int sappyou_weed(Sappyou *sappyou) {
-    if (sappyou->removed_cnt == 0) {
-        return 0;
-    }
-    uint64_t weeded_size = sappyou->size - sappyou->removed_cnt;
-    for (uint64_t i = 0, count = 0; i < sappyou->size; i++) {
-        if (sappyou->contents[i].id != 0) {
-            sappyou->contents[i - count] = sappyou->contents[i];
-        } else {
-            count++;
-        }
-    }
-    sappyou->size = weeded_size;
-    sappyou->removed_cnt = 0;
-    sappyou->contents = realloc(sappyou->contents, sappyou->size * sizeof(Tanzaku));
-    return 0;
-}
-
 int sappyou_load(Sappyou *sappyou) {
     if (sappyou->file == NULL) {
         fprintf(stderr, "Failed to load sappyou: file not specified\n");
@@ -65,12 +47,17 @@ int sappyou_load(Sappyou *sappyou) {
     sappyou->contents = malloc(sappyou->size * sizeof(Tanzaku));
     size_t max_string_len = SIZE_MAX;
     for (uint64_t i = 0; i < sappyou->size; i++) {
-        fread(&sappyou->contents[i].id, 8, 1, sappyou->file);
-        fread(&sappyou->contents[i].created_ts, 8, 1, sappyou->file);
-        fread(&sappyou->contents[i].modified_ts, 8, 1, sappyou->file);
-        getdelim(&sappyou->contents[i].name, &max_string_len, 0, sappyou->file);
-        getdelim(&sappyou->contents[i].alias, &max_string_len, 0, sappyou->file);
-        getdelim(&sappyou->contents[i].description, &max_string_len, 0, sappyou->file);
+        if (fgetc(sappyou->file) != 0) {
+            sappyou->contents[i].id = i + 1;
+            fread(&sappyou->contents[i].created_ts, 8, 1, sappyou->file);
+            fread(&sappyou->contents[i].modified_ts, 8, 1, sappyou->file);
+            getdelim(&sappyou->contents[i].name, &max_string_len, 0, sappyou->file);
+            getdelim(&sappyou->contents[i].alias, &max_string_len, 0, sappyou->file);
+            getdelim(&sappyou->contents[i].description, &max_string_len, 0, sappyou->file);
+        } else {
+            sappyou->contents[i].id = 0;
+            sappyou->removed_cnt++;
+        }
     }
     return 0;
 }
@@ -80,10 +67,6 @@ int sappyou_save(Sappyou *sappyou) {
         fprintf(stderr, "Failed to save sappyou: file not specified\n");
         return 1;
     }
-    if (sappyou_weed(sappyou) != 0) {
-        fprintf(stderr, "Failed to save sappyou: failed to weed sappyou\n");
-        return 1;
-    }
     rewind(sappyou->file);
     fwrite(SAPPYOU_SIG, 2, 4, sappyou->file);
     fwrite(&sappyou->created_ts, 8, 1, sappyou->file);
@@ -91,12 +74,19 @@ int sappyou_save(Sappyou *sappyou) {
     fwrite(&sappyou->size, 8, 1, sappyou->file);
     fflush(sappyou->file);
     for (uint64_t i = 0; i < sappyou->size; i++) {
-        fwrite(&sappyou->contents[i].id, 8, 1, sappyou->file);
-        fwrite(&sappyou->contents[i].created_ts, 8, 1, sappyou->file);
-        fwrite(&sappyou->contents[i].modified_ts, 8, 1, sappyou->file);
-        fwrite(sappyou->contents[i].name, 1, strlen(sappyou->contents[i].name) + 1, sappyou->file);
-        fwrite(sappyou->contents[i].alias, 1, strlen(sappyou->contents[i].alias) + 1, sappyou->file);
-        fwrite(sappyou->contents[i].description, 1, strlen(sappyou->contents[i].description) + 1, sappyou->file);
+        if (sappyou->contents[i].id != 0) {
+            fputc(-1, sappyou->file);
+            fwrite(&sappyou->contents[i].created_ts, 8, 1, sappyou->file);
+            fwrite(&sappyou->contents[i].modified_ts, 8, 1, sappyou->file);
+            fputs(sappyou->contents[i].name, sappyou->file);
+            fputc(0, sappyou->file);
+            fputs(sappyou->contents[i].alias, sappyou->file);
+            fputc(0, sappyou->file);
+            fputs(sappyou->contents[i].description, sappyou->file);
+            fputc(0, sappyou->file);
+        } else {
+            fputc(0, sappyou->file);
+        }
     }
     fflush(sappyou->file);
     return 0;
@@ -125,12 +115,6 @@ int tanzaku_add(Sappyou *sappyou, const char *name, const char *alias, const cha
         fprintf(stderr, "Failed to add tanzaku: sappyou is full\n");
         return 1;
     }
-    for (uint64_t i = 0; i < sappyou->size; i++) {
-        if (strcmp(name, sappyou->contents[i].name) == 0) {
-            fprintf(stderr, "Failed to add tanzaku: tanzaku with the name '%s' already exists\n", name);
-            return 1;
-        }
-    }
     Tanzaku newbie;
     newbie.created_ts = time(NULL);
     newbie.modified_ts = newbie.created_ts;
@@ -155,18 +139,20 @@ int tanzaku_add(Sappyou *sappyou, const char *name, const char *alias, const cha
 }
 
 int tanzaku_rem_by_id(Sappyou *sappyou, uint64_t tanzaku_id) {
-    if (tanzaku_id > sappyou->size) {
-        fprintf(stderr, "Failed to remove tanzaku: target tanzaku does not exist\n");
+    if (tanzaku_id == 0) {
+        fprintf(stderr, "Failed to remove tanzaku: got zero ID\n");
         return 1;
     }
-    if (sappyou->contents[tanzaku_id - 1].id == 0) {
-        fprintf(stderr, "Failed to remove tanzaku: target tanzaku is already removed\n");
-        return 1;
+    for (uint64_t i = 0; i < sappyou->size; i++) {
+        if (sappyou->contents[i].id == tanzaku_id) {
+            sappyou->modified_ts = time(NULL);
+            sappyou->contents[i].id = 0;
+            sappyou->removed_cnt++;
+            return 0;
+        }
     }
-    sappyou->modified_ts = time(NULL);
-    sappyou->contents[tanzaku_id - 1].id = 0;
-    sappyou->removed_cnt++;
-    return 0;
+    fprintf(stderr, "Failed to remove tanzaku: target tanzaku does not exist\n");
+    return 1;
 }
 
 int tanzaku_rem_by_name(Sappyou *sappyou, const char *name) {
diff --git a/src/core/sasahyou.c b/src/core/sasahyou.c
index 810542f..e03f673 100644
--- a/src/core/sasahyou.c
+++ b/src/core/sasahyou.c
@@ -1,13 +1,12 @@
 #include <malloc.h>
 #include <string.h>
 #include <time.h>
-#include <sys/stat.h>
 #include <stdio.h>
 
 #include "../../include/core.h"
 
 int sasahyou_init(Sasahyou *sasahyou) {
-    sasahyou->created_ts = time(NULL);;
+    sasahyou->created_ts = time(NULL);
     sasahyou->modified_ts = sasahyou->created_ts;
     sasahyou->size = 0;
     sasahyou->removed_cnt = 0;
@@ -27,24 +26,6 @@ int sasahyou_free(Sasahyou *sasahyou) {
     return 0;
 }
 
-int sasahyou_weed(Sasahyou *sasahyou) {
-    if (sasahyou->removed_cnt == 0) {
-        return 0;
-    }
-    uint64_t weeded_size = sasahyou->size - sasahyou->removed_cnt;
-    for (uint64_t i = 0, count = 0; i < sasahyou->size; i++) {
-        if (sasahyou->contents[i].id != 0) {
-            sasahyou->contents[i - count] = sasahyou->contents[i];
-        } else {
-            count++;
-        }
-    }
-    sasahyou->size = weeded_size;
-    sasahyou->removed_cnt = 0;
-    sasahyou->contents = realloc(sasahyou->contents, sasahyou->size * sizeof(Sasa));
-    return 0;
-}
-
 int sasahyou_load(Sasahyou *sasahyou) {
     if (sasahyou->file == NULL) {
         fprintf(stderr, "Failed to load sasahyou: file not specified\n");
@@ -64,9 +45,14 @@ int sasahyou_load(Sasahyou *sasahyou) {
     sasahyou->contents = malloc(sasahyou->size * sizeof(Sasa));
     size_t max_path_len = SIZE_MAX;
     for (uint64_t i = 0; i < sasahyou->size; i++) {
-        fread(&sasahyou->contents[i].id, 8, 1, sasahyou->file);
-        fread(&sasahyou->contents[i].created_ts, 8, 1, sasahyou->file);
-        getdelim(&sasahyou->contents[i].path, &max_path_len, 0, sasahyou->file);
+        if (fgetc(sasahyou->file) != 0) {
+            sasahyou->contents[i].id = i + 1;
+            fread(&sasahyou->contents[i].created_ts, 8, 1, sasahyou->file);
+            getdelim(&sasahyou->contents[i].path, &max_path_len, 0, sasahyou->file);
+        } else {
+            sasahyou->contents[i].id = 0;
+            sasahyou->removed_cnt++;
+        }
     }
     return 0;
 }
@@ -76,10 +62,6 @@ int sasahyou_save(Sasahyou *sasahyou) {
         fprintf(stderr, "Failed to save sasahyou: file not specified\n");
         return 1;
     }
-    if (sasahyou_weed(sasahyou) != 0) {
-        fprintf(stderr, "Failed to save sasahyou: failed to weed sasahyou\n");
-        return 1;
-    }
     rewind(sasahyou->file);
     fwrite(SASAHYOU_SIG, 2, 4, sasahyou->file);
     fwrite(&sasahyou->created_ts, 8, 1, sasahyou->file);
@@ -87,9 +69,14 @@ int sasahyou_save(Sasahyou *sasahyou) {
     fwrite(&sasahyou->size, 8, 1, sasahyou->file);
     fflush(sasahyou->file);
     for (uint64_t i = 0; i < sasahyou->size; i++) {
-        fwrite(&sasahyou->contents[i].id, 8, 1, sasahyou->file);
-        fwrite(&sasahyou->contents[i].created_ts, 8, 1, sasahyou->file);
-        fwrite(sasahyou->contents[i].path, 1, strlen(sasahyou->contents[i].path) + 1, sasahyou->file);
+        if (sasahyou->contents[i].id != 0) {
+            fputc(-1, sasahyou->file);
+            fwrite(&sasahyou->contents[i].created_ts, 8, 1, sasahyou->file);
+            fputs(sasahyou->contents[i].path, sasahyou->file);
+            fputc(0, sasahyou->file);
+        } else {
+            fputc(0, sasahyou->file);
+        }
     }
     fflush(sasahyou->file);
     return 0;
@@ -118,17 +105,6 @@ int sasa_add(Sasahyou *sasahyou, const char *path) {
         fprintf(stderr, "Failed to add sasa: sasahyou is full\n");
         return 1;
     }
-    for (uint64_t i = 0; i < sasahyou->size; i++) {
-        if (strcmp(path, sasahyou->contents[i].path) == 0) {
-            fprintf(stderr, "Failed to add sasa: file '%s' is already listed\n", path);
-            return 1;
-        }
-    }
-    struct stat st;
-    if (stat(path, &st) != 0) {
-        fprintf(stderr, "Failed to add sasa: invalid path '%s'\n", path);
-        return 1;
-    }
     Sasa newbie;
     newbie.created_ts = (uint64_t) time(NULL);
     size_t path_size = strlen(path);
@@ -144,18 +120,20 @@ int sasa_add(Sasahyou *sasahyou, const char *path) {
 }
 
 int sasa_rem_by_id(Sasahyou *sasahyou, uint64_t sasa_id) {
-    if (sasa_id > sasahyou->size) {
-        fprintf(stderr, "Failed to remove sasa: target sasa does not exist\n");
+    if (sasa_id == 0) {
+        fprintf(stderr, "Failed to remove sasa: got zero ID\n");
         return 1;
     }
-    if (sasahyou->contents[sasa_id - 1].id == 0) {
-        fprintf(stderr, "Failed to remove sasa: target sasa is already removed\n");
-        return 1;
+    for (uint64_t i = 0; i < sasahyou->size; i++) {
+        if (sasahyou->contents[i].id == sasa_id) {
+            sasahyou->modified_ts = time(NULL);
+            sasahyou->contents[i].id = 0;
+            sasahyou->removed_cnt++;
+            return 0;
+        }
     }
-    sasahyou->contents[sasa_id - 1].id = 0;
-    sasahyou->removed_cnt++;
-    sasahyou->modified_ts = time(NULL);
-    return 0;
+    fprintf(stderr, "Failed to remove sasa: target sasa does not exist\n");
+    return 1;
 }
 
 int sasa_rem_by_path(Sasahyou *sasahyou, const char *path) {
diff --git a/src/core/shoppyou.c b/src/core/shoppyou.c
index 17f3733..d820941 100644
--- a/src/core/shoppyou.c
+++ b/src/core/shoppyou.c
@@ -28,11 +28,11 @@ int shoppyou_weed(Shoppyou *shoppyou) {
         return 0;
     }
     uint64_t weeded_size = shoppyou->size - shoppyou->removed_cnt;
-    for (uint64_t i = 0, count = 0; i < shoppyou->size; i++) {
-        if (shoppyou->contents[i].sasa_id != 0 || shoppyou->contents[i].tanzaku_id != 0) {
-            shoppyou->contents[i - count] = shoppyou->contents[i];
+    for (uint64_t i = 0, shift = 0; i < shoppyou->size; i++) {
+        if (shoppyou->contents[i].sasa_id != 0 && shoppyou->contents[i].tanzaku_id != 0) {
+            shoppyou->contents[i - shift] = shoppyou->contents[i];
         } else {
-            count++;
+            shift++;
         }
     }
     shoppyou->size = weeded_size;
@@ -72,7 +72,7 @@ int shoppyou_save(Shoppyou *shoppyou) {
         return 1;
     }
     if (shoppyou_weed(shoppyou) != 0) {
-        fprintf(stderr, "Failed to save shoppyou: failed to weed sappyou\n");
+        fprintf(stderr, "Failed to save shoppyou: failed to weed shoppyou\n");
         return 1;
     }
     rewind(shoppyou->file);
@@ -113,13 +113,6 @@ int kazari_add(Shoppyou *shoppyou, uint64_t sasa_id, uint64_t tanzaku_id) {
         fprintf(stderr, "Failed to add kazari: shoppyou is full\n");
         return 1;
     }
-    for (uint64_t i = 0; i < shoppyou->size; i++) {
-        if (shoppyou->contents[i].sasa_id == sasa_id && shoppyou->contents[i].tanzaku_id == tanzaku_id) {
-            fprintf(stderr, "Failed to add kazari: kazari with sasa_id=%lu and tanzaku_id=%lu already exists\n",
-                    sasa_id, tanzaku_id);
-            return 1;
-        }
-    }
     Kazari newbie;
     newbie.created_ts = time(NULL);
     newbie.sasa_id = sasa_id;
@@ -136,7 +129,6 @@ int kazari_rem(Shoppyou *shoppyou, uint64_t sasa_id, uint64_t tanzaku_id) {
         if (shoppyou->contents[i].sasa_id == sasa_id && shoppyou->contents[i].tanzaku_id == tanzaku_id) {
             shoppyou->modified_ts = time(NULL);
             shoppyou->contents[i].sasa_id = 0;
-            shoppyou->contents[i].tanzaku_id = 0;
             shoppyou->removed_cnt++;
             return 0;
         }