as you can see the belt is slightly off. Wonder if anyone can help me on what the cause is and how to straighten/realign it.

 

Looks like you have a 2.4 L engine, but let us know what year accord you are driving.

Did you have any recent work done on your car?

The pulleys don't have adjustments and should be aligned perfectly. This likely means one pulley is out of alignment and pulling the belt off line. Try looking at the pulley alignment on each belt to see if the rest are on or off center. You can try using a straight edge across 3 pulleys edges to see eliminate/identify the out of line pulley. Obviously do with the engine not running. Repair shops have a laser to identify the culprit.

I'd take a close look at the tension pulley to see if it is pushing the belt off-line. Or any pulley that is wobbling when the engine is running, or any pulley with orange/brown dust in the center that would show wear/corrosion.

 

You are off one notch. You have to fix it on all the grooved pulleys not just the top one. Loosen it and move the belt over one notch.