a yukata; an unlined cotton kimono (for loungewear or sleepwear)
説明
A yukata is a casual cotton kimono for summer. The traditional colors are indigo and white, although recently more colorful yukata have become popular. Some people put on a yukata after having a bath and use it much like a bathrobe. It is also common to see people wearing yukata when they go out to enjoy summer festivals or public firework displays. 意訳:木綿で作った夏用の着物.色は紺と白が主流だが,最近ではカラフルな浴衣が見られるようになった.入浴後に着たり,夏祭りや花火見物などによく着られる
浴衣がけで散歩に行った
He went for a walk in his 「informal summer kimono [yukata].