Production cross section and mass excess of rare fragments produced in <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML"> <mml:mrow> <mml:mmultiscripts> <mml:mi mathvariant="normal">U</mml:mi> <mml:mprescripts/> <mml:none/> <mml:mrow> <mml:mn>

The accurate prediction of rare isotopes produced in in-flight fission of a heavy nucleus is a key question to search for new neutron-rich isotopes in the new generation of radioactive ion beam factories. Assuming that the empirical ${Q}_{g}$ scaling discovered in the projectile fragmentation reaction is obeyed in fissile fragments, i.e., the cross section of the isotopic fragment exponentially depends on its ${Q}_{g}$ value, we studied the systematic behavior of fragments produced in the in-flight fission reactions of $^{238}\mathrm{U}$ measured at RIKEN and GSI. The results show that ${Q}_{g}$ of the fissile fragment adheres to the same systematic regularity. This mechanistic universality establishes the ${Q}_{g}$-scaling method as a unified framework for predicting fragment yields across the projectile fragmentation reactions and fission reactions, providing crucial guidance for experiments searching for rare nuclei near the neutron-drip line and the nuclear structural evolution. Furthermore, using ${Q}_{g}$ values derived from the AME2020 atomic mass evaluation, the systematic behavior demonstrates robustness and allows the extraction of mass excesses from newly measured cross sections of neutron-rich isotopes. The mass excesses for 13 new isotopes, that is, $^{89}\mathrm{Ga}, ^{91,92}\mathrm{Ge}, ^{93\ensuremath{-}95}\mathrm{As}, ^{96,97}\mathrm{Se}, ^{99\ensuremath{-}101}\mathrm{Ge}$, and $^{102,103}\mathrm{Kr}$, were determined via the ${Q}_{g}$ systematics, showing consistency with the well-known mass models.