A mix of spirit and reason helped you invent the sleeve. Your spirit told you your arms were uncomfortable, stuck to your sides under that shirt. Reason told you that maybe, just maybe, if you made holes for your arms something good would come out of it. And that's how sleeves were born!
To make the sleeve holes you took your shoe (しゅう) and kicked a hole through your shirt. Then you did it again on the other side, because you have two of those weird arm things.