He has never heard Naoto laughing, Yosuke notices one day on his way back home. Of course they haven't known each other for long so he's not entirely sure but right now it seems pretty weird as well as kinda sad. Maybe she does laugh sometimes, like when she hangs out with Kanji, but still. To be honest, Yosuke has a hard time trying to figure what the sound of Naoto's laugh is like.
Yukiko's laugh, on the other hand… never ever would he have guessed she was one of these girls! 'A crazy hyena' Chie called her once. Yosuke's used to hearing her fits of laughter – it happens more and more nowadays – but he can't help feeling a little bit awkward when it happens. It can sometimes last for such a long time; and without any reason to begin with! (Souji reminds him that it is precisely why they call it a 'fit of laughter' but Yosuke makes as if he hadn't heard.)
Then again, things are different with Rise. Rise has always laughed at the slightest thing; that's a fact. She laughs when she's feeling happy, surrounded by the whole group or only one of them; she laughs with excitement when a battle goes well and when they need their personal cheerleader to root for them. She laughs again as soon as "Senpai" opens his mouth, or when he looks at her thinking that she doesn't see him. From time to time, Yosuke even finds her giggling with the other girls of the gang without any of the boys understanding why.
Women, Yosuke decides, are really way too complicated for him.
The only one that is left is Chie with her nervous laugh. Actually, she's only laughing to hide how awkward it feels when he kisses her after school. Chie is usually pretty energetic, she's always in good spirits and making her laugh isn't a difficult thing. But here it's different. It's almost as if she were rediscovering him, as if she were looking at him in a totally different way. And when she finally stops laughing, she feels her cheeks growing hot with embarrassment and now it's Yosuke's turn to laugh softly.