外亲内疏[ wài qīn nèi shū ]

⒈ 外表亲密无间，内心冷若冰霜。形容表里不一。例不料此人外亲内疏，挟诈而取益州，遂并汉中，有霸业兴隆之志。——元·关汉卿《单刀会》英close in appearance but keep a distance inside;