/usr/include/osl/ntesuki/ is in libosl-dev 0.6.0-3.1.
This file is owned by root:root, with mode 0o755.
..
/usr/include/osl/ntesuki/move_generator/
/usr/include/osl/ntesuki/move_generator/addEffect8Defense.h
/usr/include/osl/ntesuki/move_generator/captureEffectToAroundKing8.h
/usr/include/osl/ntesuki/ntesukiExceptions.h
/usr/include/osl/ntesuki/ntesukiMove.h
/usr/include/osl/ntesuki/ntesukiMove.tcc
/usr/include/osl/ntesuki/ntesukiMoveGenerator.h
/usr/include/osl/ntesuki/ntesukiMoveList.h
/usr/include/osl/ntesuki/ntesukiRecord.h
/usr/include/osl/ntesuki/ntesukiRecord.tcc
/usr/include/osl/ntesuki/ntesukiResult.h
/usr/include/osl/ntesuki/ntesukiSearcher.h
/usr/include/osl/ntesuki/ntesukiSearcher.tcc
/usr/include/osl/ntesuki/ntesukiSimulationSearcher.h
/usr/include/osl/ntesuki/ntesukiSimulationSearcherDisproof.tcc
/usr/include/osl/ntesuki/ntesukiSimulationSearcherProof.tcc
/usr/include/osl/ntesuki/ntesukiTable.h
/usr/include/osl/ntesuki/ntesukiTable.tcc
/usr/include/osl/ntesuki/oracleProverLight.h
/usr/include/osl/ntesuki/oracleProverLight.tcc
/usr/include/osl/ntesuki/readme.h
/usr/include/osl/ntesuki/rzone.h