diff --git a/src/ffi.c b/src/ffi.c
index cdf9e6e..9a724fc 100644
--- a/src/ffi.c
+++ b/src/ffi.c
@@ -159,6 +159,7 @@ extern struct static_library lib_MsgLogManager;
 extern struct static_library lib_MsgLogViewer;
 extern struct static_library lib_MsgSkip;
 extern struct static_library lib_OutputLog;
+extern struct static_library lib_PassRegister;
 extern struct static_library lib_PlayDemo;
 extern struct static_library lib_PlayMovie;
 extern struct static_library lib_SACT2;
@@ -191,6 +192,7 @@ static struct static_library *static_libraries[] = {
 	&lib_MsgLogViewer,
 	&lib_MsgSkip,
 	&lib_OutputLog,
+	&lib_PassRegister,
 	&lib_PlayDemo,
 	&lib_PlayMovie,
 	&lib_SACT2,
diff --git a/src/hll/PassRegister.c b/src/hll/PassRegister.c
new file mode 100644
index 0000000..c447f96
--- /dev/null
+++ b/src/hll/PassRegister.c
@@ -0,0 +1,266 @@
+/* Copyright (C) 2019 Nunuhara Cabbage <nunuhara@haniwa.technology>
+ *
+ * This program is free software; you can redistribute it and/or modify
+ * it under the terms of the GNU General Public License as published by
+ * the Free Software Foundation; either version 2 of the License, or
+ * (at your option) any later version.
+ *
+ * This program is distributed in the hope that it will be useful,
+ * but WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+ * GNU General Public License for more details.
+ *
+ * You should have received a copy of the GNU General Public License
+ * along with this program; if not, see <http://gnu.org/licenses/>.
+ */
+
+#include <stdio.h>
+#include <string.h>
+#include <errno.h>
+#include "cJSON.h"
+
+#include "system4.h"
+#include "system4/string.h"
+#include "system4/file.h"
+
+#include "hll.h"
+#include "xsystem4.h"
+
+/*
+ * Special SaveData API for savings sets of integers and strings
+ * (e.g. unlocked CGs).
+ */
+
+struct passregister {
+	char *filename;
+	size_t nr_integers;
+	int *integers;
+	size_t nr_strings;
+	char **strings;
+};
+
+static size_t nr_registers = 0;
+static struct passregister *registers = NULL;
+
+static cJSON *register_to_json(unsigned handle)
+{
+	struct passregister *reg = registers + handle;
+	cJSON *obj = cJSON_CreateObject();
+	cJSON *integers = cJSON_CreateArray();
+	cJSON *strings = cJSON_CreateArray();
+
+	for (size_t i = 0; i < reg->nr_integers; i++) {
+		cJSON_AddItemToArray(integers, cJSON_CreateNumber(reg->integers[i]));
+	}
+	for (size_t i = 0; i < reg->nr_strings; i++) {
+		cJSON_AddItemToArray(strings, cJSON_CreateString(reg->strings[i]));
+	}
+
+	cJSON_AddItemToObject(obj, "integers", integers);
+	cJSON_AddItemToObject(obj, "strings", strings);
+	return obj;
+}
+
+static void write_register(unsigned handle)
+{
+	struct passregister *reg = registers + handle;
+
+	FILE *f = fopen(reg->filename, "wb");
+	if (!f) {
+		WARNING("Failed to open PassRegister file: %s: %s", reg->filename, strerror(errno));
+		return;
+	}
+
+	cJSON *json = register_to_json(handle);
+	char *str = cJSON_Print(json);
+	if (fwrite(str, strlen(str), 1, f) != 1) {
+		WARNING("Failed to write PassRegister file: %s: %s", reg->filename, strerror(errno));
+		goto end;
+	}
+	if (fclose(f)) {
+		WARNING("Error writing to save file: %s: %s", reg->filename, strerror(errno));
+		goto end;
+	}
+end:
+	free(str);
+	cJSON_Delete(json);
+}
+
+static cJSON *_type_check(const char *file, const char *func, int line, int type, cJSON *json)
+{
+	if (!json || json->type != type)
+		_vm_error("*ERROR*(%s:%s:%d): Invalid PassRegister save file", file, func, line);
+	return json;
+}
+
+#define type_check(type, json) _type_check(__FILE__, __func__, __LINE__, type, json)
+
+static void read_register(unsigned handle, const char *filename)
+{
+	struct passregister *reg = registers + handle;
+	reg->filename = savedir_path(filename);
+
+	size_t data_len;
+	char *data = file_read(reg->filename, &data_len);
+	if (data) {
+		// parse/validate JSON data
+		cJSON *obj = type_check(cJSON_Object, cJSON_Parse(data));
+		cJSON *integers = type_check(cJSON_Array, cJSON_GetObjectItem(obj, "integers"));
+		cJSON *strings = type_check(cJSON_Array, cJSON_GetObjectItem(obj, "strings"));
+
+		reg->nr_integers = cJSON_GetArraySize(integers);
+		reg->integers = xcalloc(reg->nr_integers, sizeof(int));
+		for (size_t i = 0; i < reg->nr_integers; i++) {
+			cJSON *value = type_check(cJSON_Number, cJSON_GetArrayItem(integers, i));
+			reg->integers[i] = value->valueint;
+		}
+		reg->nr_strings = cJSON_GetArraySize(strings);
+		reg->strings = xcalloc(reg->nr_strings, sizeof(char*));
+		for (size_t i = 0; i < reg->nr_strings; i++) {
+			cJSON *value = type_check(cJSON_String, cJSON_GetArrayItem(strings, i));
+			reg->strings[i] = strdup(cJSON_GetStringValue(value));
+		}
+
+		cJSON_Delete(obj);
+	}
+}
+
+static bool PassRegister_SetFileName(int handle, struct string *filename)
+{
+	if (handle < 0)
+		return false;
+	if ((size_t)handle >= nr_registers) {
+		registers = xrealloc_array(registers, nr_registers, handle+1, sizeof(struct passregister));
+	}
+	read_register(handle, filename->text);
+	return true;
+}
+
+static bool exist_number(int handle, int n)
+{
+	// NOTE: this could be improved by sorting the array
+	struct passregister *reg = registers + handle;
+	for (size_t i = 0; i < reg->nr_integers; i++) {
+		if (reg->integers[i] == n)
+			return true;
+	}
+	return false;
+}
+
+static bool PassRegister_RegistNumber(int handle, int n)
+{
+	if (handle < 0 || (size_t)handle >= nr_registers || !registers[handle].filename)
+		return false;
+	if (exist_number(handle, n))
+		return true;
+
+	struct passregister *reg = registers + handle;
+	reg->integers = xrealloc_array(reg->integers, reg->nr_integers, reg->nr_integers+1, sizeof(int));
+	reg->integers[reg->nr_integers++] = n;
+	write_register(handle);
+	return true;
+}
+
+static bool exist_text(int handle, const char *text)
+{
+	// NOTE: this could be improved by sorting the array
+	struct passregister *reg = registers + handle;
+	for (size_t i = 0; i < reg->nr_strings; i++) {
+		if (!strcmp(reg->strings[i], text))
+			return true;
+	}
+	return false;
+}
+
+static bool PassRegister_RegistText(int handle, struct string *text)
+{
+	if (handle < 0 || (size_t)handle >= nr_registers || !registers[handle].filename)
+		return false;
+	if (exist_text(handle, text->text))
+		return true;
+
+	struct passregister *reg = registers + handle;
+	reg->strings = xrealloc_array(reg->strings, reg->nr_strings, reg->nr_strings+1, sizeof(char*));
+	reg->strings[reg->nr_strings++] = strdup(text->text);
+	write_register(handle);
+	return true;
+}
+
+static bool PassRegister_UnregistNumber(int handle, int n)
+{
+	if (handle < 0 || (size_t)handle >= nr_registers || !registers[handle].filename)
+		return false;
+
+	struct passregister *reg = registers + handle;
+	for (size_t i = 0; i < reg->nr_integers; i++) {
+		if (reg->integers[i] != n)
+			continue;
+		for (size_t j = i+1; j < reg->nr_integers; j++) {
+			reg->integers[j-1] = reg->integers[j];
+		}
+		reg->nr_integers--;
+		write_register(handle);
+	}
+	return true;
+}
+
+static bool PassRegister_UnregistText(int handle, struct string *text)
+{
+	if (handle < 0 || (size_t)handle >= nr_registers || !registers[handle].filename)
+		return false;
+
+	struct passregister *reg = registers + handle;
+	for (size_t i = 0; i < reg->nr_strings; i++) {
+		if (strcmp(reg->strings[i], text->text))
+			continue;
+		for (size_t j = 0; j < reg->nr_strings; j++) {
+			reg->strings[j-1] = reg->strings[j];
+		}
+		reg->nr_strings--;
+		write_register(handle);
+	}
+	return true;
+}
+
+static bool PassRegister_UnregistAll(int handle)
+{
+	if (handle < 0 || (size_t)handle >= nr_registers || !registers[handle].filename)
+		return false;
+
+	struct passregister *reg = registers + handle;
+	if (!reg->nr_integers && !reg->nr_strings)
+		return true;
+
+	free(reg->integers);
+	free(reg->strings);
+	reg->integers = NULL;
+	reg->strings = NULL;
+	reg->nr_integers = 0;
+	reg->nr_strings = 0;
+	write_register(handle);
+	return true;
+}
+
+static bool PassRegister_ExistNumber(int handle, int n)
+{
+	if (handle < 0 || (size_t)handle >= nr_registers || !registers[handle].filename)
+		return false;
+	return exist_number(handle, n);
+}
+
+static bool PassRegister_ExistText(int handle, struct string *text)
+{
+	if (handle < 0 || (size_t)handle >= nr_registers || !registers[handle].filename)
+		return false;
+	return exist_text(handle, text->text);
+}
+
+HLL_LIBRARY(PassRegister,
+	    HLL_EXPORT(SetFileName, PassRegister_SetFileName),
+	    HLL_EXPORT(RegistNumber, PassRegister_RegistNumber),
+	    HLL_EXPORT(RegistText, PassRegister_RegistText),
+	    HLL_EXPORT(UnregistNumber, PassRegister_UnregistNumber),
+	    HLL_EXPORT(UnregistText, PassRegister_UnregistText),
+	    HLL_EXPORT(UnregistAll, PassRegister_UnregistAll),
+	    HLL_EXPORT(ExistNumber, PassRegister_ExistNumber),
+	    HLL_EXPORT(ExistText, PassRegister_ExistText));
diff --git a/src/meson.build b/src/meson.build
index b2f2d6f..8095ac8 100644
--- a/src/meson.build
+++ b/src/meson.build
@@ -39,6 +39,7 @@ xsystem4 = ['audio.c',
             'hll/MsgLogViewer.c',
             'hll/MsgSkip.c',
             'hll/OutputLog.c',
+            'hll/PassRegister.c',
             'hll/PlayDemo.c',
             'hll/PlayMovie.c',
             'hll/SACT2.c',
diff --git a/subprojects/libsys4 b/subprojects/libsys4
index 7b08a56..9c1b705 160000
--- a/subprojects/libsys4
+++ b/subprojects/libsys4
@@ -1 +1 @@
-Subproject commit 7b08a56babe700fdcc07cc3bdbd0132a55733a84
+Subproject commit 9c1b705830c50e1605250a2898096b02f52eb172