灯台下暗し (とうだいもとくらし): it is darkest under the lamp post; it's hard to see what is under your nose

it is darkest under the lamp post; it's hard to see what is under your nose

An oil lamp lights the room but leaves its own base in shadow. Said when the answer, the missing keys, or the obvious candidate was sitting right beside you the whole time.

A Japanese proverb (ことわざ)