WatcherCCG said: Are we sure that's a pattern and not Suwako actually sitting on the shirt?
If Suwako was sitting on the shirt, there would be a bunch more wrinkles around where her weight would be resting. If Suwako was sitting in the shirt and it was transparent, we'd be able to see some of the reverse details. No, that's clearly a pattern screened on the front of the shirt.
However, one wonders why the shirt is standing up with no visible means of support. Being that it's Ao Usagi, I wouldn't put it past him to have Suwako sitting inside the shirt in the same pose. Then again, with Ao Usagi, it's never what you'd expect.