noun
red ink paste; seal ink; vermillion ink pad
Thick red ink used with Japanese personal seals (hanko/inkan). Often refers to the ink paste itself or the pad containing it.
朱肉が乾いてきたので、新しいのを買わないといけない。
The red ink paste is drying out, so I need to buy a new one.
契約書に印鑑を押す前に、朱肉をつけてください。
Please apply red ink paste to the seal before stamping the contract.