Nitrogenous heterocyclic compound represented by formula (VI), or a salt thereof: wherein R represents a group represented by CR1R2R3 or a cyano group； R1 to R3 respectively and independently represent a hydrogen atom, an unsubstituted C1-8 alkyl group, a C1-8 cycloalkylalkyl group, a C1-8 cycloalkenyl alkyl group, a C1-8 haloalkyl group, an aryl group C 1-8 alkyl, a heteroaryl-C 1-8 alkyl group, a hydroxyl-C 1-8 alkyl group, a C 1-8 alkoxy-alkyl group, a C 1-8 acyloxy-alkyl group, a trialkylsilyloxy- C1-8 alkyl, an arylsulfonyloxy-C1-8 alkyl group, a cyano-C1-8 alkyl group, a C1-8 acyl-alkyl group, a C1-8 2-hydroxyimino-alkyl group, a C1-8 carboxy-alkyl group, a C1-8 alkoxycarbonyl-alkyl group, a C1-8 alkyl-alkyl group, an unsubstituted C2-8 alkenyl group, an unsubstituted C2-8 alkynyl group, a unsubstituted C3-8 cycloalkyl group, an unsubstituted C4-8 cycloalkenyl group, an unsubstituted C6-10 aryl group, an unsubstituted heterocyclic group, an unsubstituted C1-8 acyl group, a group (1- imi no) unsubstituted C1-8 alkyl, an unsubstituted carboxyl group, an alkoxycarbonyl group, an unsubstituted carbamoyl group, a monoalkylcarbamoyl group, a dialkylcarbamoyl group, a monoarylcarbamoyl group, a hydroxyl group, an alkoxy group, a cycloalkylalkoxy group, an aralkyloxy group, a haloalkoxy group, an alkenyloxy group, an alkynyloxy group, a cycloalkyloxy group, an aryloxy group, an arylalkyloxy group, an acyloxy group, an alkoxycarbonylalkyl group, a trialkylsilyloxy group, an unsubstituted amino group, a non-mercapto group substituted, a sulfonyl group, a halogen group, a cyano group or a nitro group, with the proviso that R1 to R3 are not all hydrogen atoms, R1 to R3 are not all unsubstituted C1-8 alkyl groups； in any case R1 to R3 is a hydrogen atom, the remaining two are not unsubstituted C1-8 alkyl groups； in any case R1 to R3 is an unsubstituted C1-8 alkyl group, the remaining two are not hydrogen atoms, X1 respectively and independently represents an unsubstituted
