请不要忽略这里的异步行为。在循环之后在回调函数中发送响应。

var list = [
    {
        title: '', 
        author: '',
        content: ''
    }
]

router.get('/japan', function (req, res) {
    var sql = 'select * from japan';
    conn.query(sql, function (err, rows, fields) {
        for (var i = 0; i < rows.length; i++) {
            list[i] = {
                title: rows[i].title,
                author: rows[i].author,
                Content: rows[i].content
            }
        }
        res.render('menu/japan/jp', {
            status: req.signedCookies.login_status,
            lists: list
        });
    });
});