noun
covert ninja operations; stealthy infiltration
Historical term for a ninja carrying out secret missions while remaining unseen. Contrasts with 陽忍 (ようにん), which involves open disguise or social infiltration.
See also: 陽忍
陰忍は、姿を隠して任務を遂行する忍者のことだ。
Innin refers to a ninja who carries out missions while staying hidden.
忍者には陽忍と陰忍の二つの働き方
There were two ways of operating for ninja: yōnin and innin.