Abstract: A single-stranded antisense oligonucleotide, or a pharmaceutically acceptable salt thereof, capable of modulating expression and/or function of RPS25 gene, wherein nucleotides of the single-stranded antisense oligonucleotide are bonded to each other via a phosphate group and/or a modified phosphate group, the single-stranded antisense oligonucleotide includes a gap region, a 3? wing region bonded to a 3? end of the gap region, and a 5? wing region bonded to a 5? end of the gap region, the gap region is a deoxyribose-based nucleic acid optionally including a nucleic acid having a modified sugar moiety, each of the 3? wing region and the 5? wing region is a modified nucleotide, the single-stranded antisense oligonucleotide has a base length of 12- to 30-mer, and a base sequence of the antisense oligonucleotide is: a base sequence with a sequence identity of 90% to 100% to a base sequence complementary to at least one target region of the same base length as the antisense oligonucleotide present in the base sequ