A compound of the formula or a salt thereof: wherein Y is N or CR 1, R 1, R 3, and R 4 are the same as or different from each other and are each C 1-6 alkyl which may be substituted with one or more substituents selected from the group consisting of halogen, -OH, -O-C 1-6 alkyl, -O-halogeno-C 1-6 alkyl and -NR 9 R 10, H, or halogen, R 2 is C 1-6 alkyl which may be substituted with one or more substituents selected from the group consisting of halogen and cyano, and R 2 may be combined with R 1 to form -(CH 2) n -, or R 2 may be combined with R 3 to form -(CH 2) n -, n is 2 or 3, R 51 and R 52 are the same as or different from each other and are C 1-6 alkyl which may be substituted with one or more substituents selected from Group G 2, cycloalkyl which may be substituted with one or more substituents selected from Group G 1, or H, and further, R 51 and R 52 may be combined with a nitrogen atom to which they are bonded to form cyclic amino which may be substituted with one or more substituents selected from Group G 1, X is a bond, -NR 11 -, or -NMR 11 -O-, R 11 is H or C 1-6 alkyl, R 6 is C 1-6 alkyl which may be substituted with one or more substituents selected from Group G 4, or cycloalkyl which may be substituted with one or more substituents selected from Group G 3, further, when -X-R 6 - is NR 11 -R 6, R 6 and R 11 may be combined with a nitrogen atom to which they are bonded to form cyclic amino which may be substituted with one or more substituents selected from Group G 3, R 7 and R 8 are the same as or different from each other and are each C 1-6 alkyl which may be substituted with one or more substituents selected from the group consisting of halogen, -OH, and -O-halogeno-C 1-6 alkyl, or H, Group G 1 and Group G 3 include C 1-6 alkyl, halogeno-C 1-6 alkyl, halogen, -OH,-O-C 1-6 alkyl, -O-halogeno-C 1-6 alkyl, and -NR 9 R 10, Group G 2 and Group G 4 include halogen, -OH, -O-C 1-6 alkyl, -O-halogeno-C 1-6 alkyl, cycloalkyl which may be substituted with one or more halogen atoms, -O-(cycloalkyl which may be substituted with one or more halogen atoms), and -NR 9 R 10, and R 9 and R 10 are the same as or different from each other and are H or C 1-6 alkyl. Y is N or CR 1, R 1, R 3, and R 4 are the same as or different from each other and are each C 1-6 alkyl which may be substituted with one or more substituents selected from the group consisting of halogen, -OH, -O-C 1-6 alkyl, -O-halogeno-C 1-6 alkyl and -NR 9 R 10, H, or halogen, R 2 is C 1-6 alkyl which may be substituted with one or more substituents selected from the group consisting of halogen and cyano, and R 2 may be combined with R 1 to form -(CH 2) n -, or R 2 may be combined with R 3 to form -(CH 2) n -, n is 2 or 3, R 51 and R 52 are the same as or different from each other and are C 1-6 alkyl which may be substituted with one or more substituents selected from Group G 2, cycloalkyl which may be substituted with one or more substituents selected from Group G 1, or H, and further, R 51 and R 52 may be combined with a nitrogen atom to which they are bonded to form cyclic amino which may be substituted with one or more substituents selected from Group G 1, X is a bond, -NR 11 -, or -NMR 11 -O-, R 11 is H or C 1-6 alkyl, R 6 is C 1-6 alkyl which may be substituted with one or more substituents selected from Group G 4, or cycloalkyl which may be substituted with one or more substituents selected from Group G 3, further, when -X-R 6 - is NR 11 -R 6, R 6 and R 11 may be combined with a nitrogen atom to which they are bonded to form cyclic amino which may be substituted with one or more substituents selected from Group G 3, R 7 and R 8 are the same as or different from each other and are each C 1-6 alkyl which may be substituted with one or more substituents selected from the group consisting of halogen, -OH, and -O-halogeno-C 1-6 alkyl, or H, Group G 1 and Group G 3 include C 1-6 alkyl, halogeno-C 1-6 alkyl, halogen, -OH,-O-C 1-6 alkyl, -O-halogeno-C 1-6 alkyl, and -NR 9 R 10, Group G 2 and Group G 4 include halogen, -OH, -O-C 1-6 alkyl, -O-halogeno-C 1-6 alkyl, cycloalkyl which may be substituted with one or more halogen atoms, -O-(cycloalkyl which may be substituted with one or more halogen atoms), and -NR 9 R 10, and R 9 and R 10 are the same as or different from each other and are H or C 1-6 alkyl.