In MS-IME, The conversion candidate window appears in a wrong position for the text field being entered. This occurs when using OpenJDK8 on Windows. I found the problem using jdk8u422 on Windows 10.

You can reproduce the problem by running the following test:

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import java.awt.Frame;
import java.awt.GridLayout;
import java.awt.Panel;
import java.awt.SystemColor;
import java.awt.Window;

import javax.swing.JTextField;

public class TP extends Frame {

    public TP() {
        this.setBounds(-100, -100, 0, 0);
        this.setVisible(true);

        SubWindow w = new SubWindow(this);
        w.setVisible(true);
    }

    public static void main(String[] args) {
        TP TP = new TP();
    }

    class SubWindow extends Window {
        public SubWindow(Frame f) {
            super(f);
            this.setFocusable(true);
            this.setBackground(SystemColor.red);
            this.setBounds(0, 0, 1032, 795);
            this.setLayout(new GridLayout(1, 2));

            this.add(new Panel());

            Panel p = new Panel();
            p.setLayout(null);

            JTextField tf = new JTextField();
            tf.setBounds(10, 270, 300, 30);
            p.add(tf);
            this.add(p);

        }
    }
}
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How to Reproduced:
1. Go to "Language Preferences -> Add a Language" and add "Japanese"
2. Set current IM to "Japanese"
3. java TP
4. Type 'a' multiple times into TextField and the conversion candidate window appears.

Expected:
The candidate window appears at the bottom or top adjacent to the text field.
See attachment TP_jdk21.png using JDK21.

Actual:
The candidate window appears in the wrong position over the text field.
See attachment TP_jdk8.png using JDK8.

The cause of this problem may be an insufficient fix in JDK-8076455.
Similar issues, JDK-8202084 and JDK-8189687, have been reported and fixed in JDK9.