This study aims to explore Neotermes sugioi's sex chromosomes and conduct karyotype analysis. The termites, found on Okinawa's main island and the Sakishima Islands, exhibit unique traits like a male-biased sex allocation . Previous research has identified a potential sex determination gene, Sym. However, sex determination genes in hemimetabolous insects have remained elusive. To address this, we prepared high-quality chromosome specimens from both male and female reproductive organs and ganglia. We performed basic karyotype analysis and explored the sex chromosomes. Additionally, we conducted FISH mappings of telomere sequences and 18S rRNA genes. Our findings revealed that the sex chromosomes are the second-largest chromosomes in this species. The Y chromosome appears telocentric with a shortened short arm, indicating significant differentiation. C-band staining detected heterochromatinization, a typical feature of sex chromosomes. Furthermore, FISH analysis unveiled that the telomere signals were significantly different between sexes. This difference in telomere sequence length between males and females may suggest their distinct lifespans. This phenomenon remains unprecedented in any organism, and the genetic mechanisms underlying it remain unclear. Understanding this phenomenon could lead to breakthroughs not only in sex determination but also in lifespan-related mechanisms.