expression
wearing nothing but underpants
Describes a state of undress where the person is wearing only a single pair of underpants, often used in casual or humorous contexts.
朝起きたら、彼はパンツ一枚でリビングにいた。
When I woke up in the morning, he was in the living room wearing nothing but his underpants.
パンツ一枚で外に出るのはやめてください。
Please don't go outside in just your underpants.