隠密: Stealthy, covert, undercover.

隠密: Stealth; a spy or undercover detective.

skill (capacity to do something well)

to use / to employ / to make use of, to apply / to spend

penetration / invasion / trespassing

to invade / to break in / to trespass

stealthy, covert, undercover

stealth / A spy or undercover detective. In former times, included warriors or ninja sent to gather information.

base (e.g. military, research)

(intent slang) Clipping of 基地外 (kichigai, “madness; insanity; enthusiasm”).