<p>The age, growth, and maturation of <i>Loliolus japonicus</i> were studied using samples collected in Sendai Bay from July 2020 to December 2024. A logistic growth equation was calculated to examine the relationship between age and dorsal mantle length. Since the mature size of squids differed by hatching month, growth equations were estimated for two cohorts with different hatching seasons. The growth equations obtained showed a significant difference between males and females, with females growing faster than males. Using statolith microstructure, the hatching periods of <i>L. japonicus</i> spanned the whole year, with most hatching occurring between May and September. The lifespan of <i>L. japonicus</i> was previously thought to be 1 year, but as a result of statolith microstructure analysis in this study, it was revealed that males live up to only 8 months and females to a maximum of 9 months.</p>