血の巡りの悪い
Meanings
1
dim-witted; slow on the uptake
Idiomatic expression literally meaning 'poor circulation of blood (to the head)', used to describe someone who is slow to understand or not very sharp.
He's a dim-witted guy; no matter how many times you explain, he doesn't get it.
With someone slow on the uptake, you have to be blunt or they won't understand.