@trapsarebetter Yes I agree that any wide enough shirt works. That doesn't mean that Kaoru has wide enough shirts. If he wanted to actually dress as a girl he'd have more clothes but he only does it because of her parents so he doesn't need to have wide shirts.
@katelyngadd Depends on how often he visits. If it's like once a month, it wouldn't be that odd that he ended up wearing the same outfit every time. If it's once a week, yeah, she's definitely noticed. But there's other hints that she's figured out he's a boy and that her daughter likes him, so she's not going to say anything.
@trapsarebetter I had a look at the chapter again. She paid for the outfit so it's not too much of a stretch to assume that he returned the outfit to her after. He doesn't want to have to explain to his parents why he bought a dress after all.
LOL I can imagine a few different scenarios with the mom
1. She knows that he's actually a guy and ships them
2. She thinks he's a girl and ships them both as yuri LOOL
3. None of the above