Window pattern upside down.
Seriously, what the shit
what if the pattern isn't a pattern and it's actually a picture of something like a cat, since sprites are so small, it was impossible to make it anything legible
That would make sense, but I think Mado's name literally means 'window.' So yeah
Still, her name doesn't really prove her shirt designs meaning.
But since all we have to work off of is the sprite the logo on her shirt is either a generic checkered pattern or a window. I think a window is cooler than a generic checkered pattern.
It could have been an extremely pixel-y heart.
Or, a censor bar, to represent covering up a dark past.
What if it's the mickey mouse symbol?