Blow
You attempt to expel wind out of your mouth but lack the breath to blow out any. You’re using your mouth and trying to blow out some air, but you are failing to do so.
Blow some air out of your mouth. It’s easy, right? Imagine what could cause you to fail at this activity.
すい
ふ
None
You silly fool (ふ), the reason you couldn’t blow any air out of your mouth is because your hand was over it. You can’t blow air out that way. You silly fool, you.
Attempt to blow air out of your mouth while covering it with your hand. It’s hard to do, right? Only a fool would try to blow air out of their mouth this way.