diff --git a/include/mcl/ec.hpp b/include/mcl/ec.hpp
index 8cf3a49..ee74779 100644
--- a/include/mcl/ec.hpp
+++ b/include/mcl/ec.hpp
@@ -752,6 +752,23 @@ public:
 		}
 		EcT P(*this);
 		P.normalize();
+		if (ioMode & IoEcAffineSerialize) {
+			if (b_ == 0) { // assume Zero if x = y = 0
+				*pb = false;
+				return;
+			}
+			if (isZero()) {
+				// all zero
+				P.z.save(pb, os, IoSerialize);
+				if (!*pb) return;
+				P.z.save(pb, os, IoSerialize);
+				return;
+			}
+			P.x.save(pb, os, IoSerialize);
+			if (!*pb) return;
+			P.y.save(pb, os, IoSerialize);
+			return;
+		}
 		if (ioMode & (IoSerialize | IoSerializeHexStr)) {
 			const size_t n = Fp::getByteSize();
 			const size_t adj = isMSBserialize() ? 0 : 1;
@@ -835,6 +852,21 @@ public:
 #else
 		z = 1;
 #endif
+		if (ioMode & IoEcAffineSerialize) {
+			if (b_ == 0) { // assume Zero if x = y = 0
+				*pb = false;
+				return;
+			}
+			x.load(pb, is, IoSerialize);
+			if (!*pb) return;
+			y.load(pb, is, IoSerialize);
+			if (!*pb) return;
+			if (x.isZero() && y.isZero()) {
+				z.clear();
+				return;
+			}
+			goto verifyValidness;
+		}
 		if (ioMode & (IoSerialize | IoSerializeHexStr)) {
 			const size_t n = Fp::getByteSize();
 			const size_t adj = isMSBserialize() ? 0 : 1;
@@ -917,10 +949,7 @@ public:
 			x.load(pb, is, ioMode); if (!*pb) return;
 			if (c == '1') {
 				y.load(pb, is, ioMode); if (!*pb) return;
-				if (!isValid(x, y)) {
-					*pb = false;
-					return;
-				}
+				goto verifyValidness;
 			} else if (c == '2' || c == '3') {
 				bool isYodd = c == '3';
 				*pb = getYfromX(y, x, isYodd);
@@ -941,6 +970,13 @@ public:
 		} else {
 			*pb = true;
 		}
+		return;
+	verifyValidness:
+		if (!isValid(x, y)) {
+			*pb = false;
+			return;
+		}
+		goto verifyOrder;
 	}
 	// deplicated
 	static void setCompressedExpression(bool compressedExpression = true)
diff --git a/include/mcl/fp.hpp b/include/mcl/fp.hpp
index 894d939..d49fd45 100644
--- a/include/mcl/fp.hpp
+++ b/include/mcl/fp.hpp
@@ -263,7 +263,7 @@ public:
 	{
 		bool isMinus = false;
 		*pb = false;
-		if (ioMode & (IoArray | IoArrayRaw | IoSerialize | IoSerializeHexStr)) {
+		if (fp::isIoSerializeMode(ioMode)) {
 			const size_t n = getByteSize();
 			v_[op_.N - 1] = 0;
 			size_t readSize;
@@ -299,7 +299,7 @@ public:
 	void save(bool *pb, OutputStream& os, int ioMode) const
 	{
 		const size_t n = getByteSize();
-		if (ioMode & (IoArray | IoArrayRaw | IoSerialize | IoSerializeHexStr)) {
+		if (fp::isIoSerializeMode(ioMode)) {
 			if (ioMode & IoArrayRaw) {
 				cybozu::write(pb, os, v_, n);
 			} else {
diff --git a/include/mcl/op.hpp b/include/mcl/op.hpp
index d6132a4..021d415 100644
--- a/include/mcl/op.hpp
+++ b/include/mcl/op.hpp
@@ -101,11 +101,17 @@ enum IoMode {
 	IoSerialize = 512, // use MBS for 1-bit y
 	IoFixedSizeByteSeq = IoSerialize, // obsolete
 	IoEcProj = 1024, // projective or jacobi coordinate
-	IoSerializeHexStr = 2048 // printable hex string
+	IoSerializeHexStr = 2048, // printable hex string
+	IoEcAffineSerialize = 4096 // serialize [x:y]
 };
 
 namespace fp {
 
+inline bool isIoSerializeMode(int ioMode)
+{
+	return ioMode & (IoArray | IoArrayRaw | IoSerialize | IoEcAffineSerialize | IoSerializeHexStr);
+}
+
 const size_t UnitBitSize = sizeof(Unit) * 8;
 
 const size_t maxUnitSize = (MCL_MAX_BIT_SIZE + UnitBitSize - 1) / UnitBitSize;
@@ -366,7 +372,7 @@ private:
 
 inline const char* getIoSeparator(int ioMode)
 {
-	return (ioMode & (IoArray | IoArrayRaw | IoSerialize | IoSerializeHexStr)) ? "" : " ";
+	return (ioMode & (IoArray | IoArrayRaw | IoSerialize | IoSerializeHexStr | IoEcAffineSerialize)) ? "" : " ";
 }
 
 inline void dump(const void *buf, size_t n)
diff --git a/test/bls12_test.cpp b/test/bls12_test.cpp
index fe0ca7a..df8b127 100644
--- a/test/bls12_test.cpp
+++ b/test/bls12_test.cpp
@@ -104,7 +104,7 @@ void pairingC(Fp12& e, const G1& P, const G2& Q)
 void testIoAll(const G1& P, const G2& Q)
 {
 	const int FpTbl[] = { 0, 2, 2|mcl::IoPrefix, 10, 16, 16|mcl::IoPrefix, mcl::IoArray, mcl::IoArrayRaw };
-	const int EcTbl[] = { mcl::IoEcAffine, mcl::IoEcProj, mcl::IoEcCompY, mcl::IoSerialize };
+	const int EcTbl[] = { mcl::IoEcAffine, mcl::IoEcProj, mcl::IoEcCompY, mcl::IoSerialize, mcl::IoEcAffineSerialize };
 	for (size_t i = 0; i < CYBOZU_NUM_OF_ARRAY(FpTbl); i++) {
 		for (size_t j = 0; j < CYBOZU_NUM_OF_ARRAY(EcTbl); j++) {
 			G1 P2 = P, P3;
diff --git a/test/bn_test.cpp b/test/bn_test.cpp
index 15f6f45..e6139b3 100644
--- a/test/bn_test.cpp
+++ b/test/bn_test.cpp
@@ -338,7 +338,7 @@ void testTrivial(const G1& P, const G2& Q)
 void testIoAll(const G1& P, const G2& Q)
 {
 	const int FpTbl[] = { 0, 2, 2|mcl::IoPrefix, 10, 16, 16|mcl::IoPrefix, mcl::IoArray, mcl::IoArrayRaw };
-	const int EcTbl[] = { mcl::IoEcAffine, mcl::IoEcProj, mcl::IoEcCompY, mcl::IoSerialize };
+	const int EcTbl[] = { mcl::IoEcAffine, mcl::IoEcProj, mcl::IoEcCompY, mcl::IoSerialize, mcl::IoEcAffineSerialize };
 	for (size_t i = 0; i < CYBOZU_NUM_OF_ARRAY(FpTbl); i++) {
 		for (size_t j = 0; j < CYBOZU_NUM_OF_ARRAY(EcTbl); j++) {
 			G1 P2 = P, P3;