noun, noun which may take the genitive case particle 'no'
direct line of descent; direct lineage
Refers to a direct bloodline or succession without branching, such as parent-to-child. Often used in legal, historical, or family contexts.
彼は徳川家の直系の子孫だ。
He is a direct descendant of the Tokugawa family.
Only direct-line relatives become heirs.
He is said to be a direct descendant of that warlord.
That fortune has been passed down through the direct line of descent.