lights are on but no one home
何も考えていない人、頭の悪い人
Ex
- I tried all to understand him, but the lights are on but nobody is home.
- He studied about it but the lights are on nobody is home.
Reference source
- https://ejje.weblio.jp/content/lights+on+but+no+one+home
- https://idioms.thefreedictionary.com/The+lights+are+on+but+nobody%27s-one%27s+home
- https://www.theidioms.com/lights-are-on-but-nobody-is-home/