>>9368683The elastic band is from the pants but it looks like the shirt due to the way they did it so low and as its own part. It's pretty much the same costume as the Buu saga but sometimes the Buu saga one was really tight and sometimes it wasn't. The manga was the same way only you never see the cut between his shirt and pants, only can infer it due to him not having his shirt on earlier and some tightness like he's wearing a belt or elastic band.
https://youtu.be/lQUo1DaaZTA