The Japanese Ministry of Health, Labor and Welfare (MHLW) designated four flavoring substances as legally permitted for use in flavorings in Japan. (Supporting documents posted here in Japanese.)
The approved flavoring substances are:
(3-Amino-3-carboxypropyl) dimethylsulfonium chloride (CAS# 3493-12-7) ([FEMA# 3445 = CAS# 111-84-0 and dl-(3-Amino-3-carboxypropyl) dimethylsulfonium chloride], [JECFA 1427 = DL-(3-Amino-3- carboxypropyl)dimethylsulfonium chloride], [FL 17.015 = CAS# 1115-84-0 and S-Methylmethioninesulphonium chloride])
2-Ethyl-6-methylpyrazine (CAS# 36731-41-6) ([FEMA# 3919 = CAS 13925-03-6], [JECFA 769 = CAS 13925-03-6], [FL 14.114 = CAS# 13925-03-6])
Trimethylamine (CAS# 75-50-3) (FEMA# 3241, JECFA 1610, FL 11.009)
trans-2-Methyl-2-butenal (CAS# 497-03-0) ([FEMA# 3407 = 2-Methyl-2-butenal], [JECFA 1201 = 2-Methyl-2-butenal], [FL 05.095 = 2-Methylcrotonaldehyde])
