Ok, that manga have now officially thought me something new. I have no idea that "onani" came from a Biblical character. I didn't even know that character existed, much less associating it to a Japanese word.
For the longest time erudite people have snarkily referred to masturbation as "the sin of Onan".
Which is nonsense. Onan's sin was that god directly told him to get his sister in law pregnant, and he was like "nah fam", which god reacted to in his usual extremely reasonable and mature fashion by murdering him dead.
Yeah, this one didn't really land for me. There wasn't enough to show that they were childhood friends or that they were reconnecting after years of separation; you could substitute any number of different backgrounds and have them fit with little issue. Unfortunately, without that extra depth or emotional component, it's just the same two panels repeating, over and over again, in service of a joke that can't land without a twist that they don't have.
The twist is that she's a Pokémon and that's literally all she can say.
How would a girl crossdress anyway? There isn't really a lot of "masculine-gender-locked" clothing anymore. A suit or tuxedo (with a suit jacket, not a blazer) comes to mind, maybe a shirt, everything else, meanung most everyday clothing men wear, is unisex. Unlike skirts and dresses, which are (with very few exceptions) locked to the feminine. Blouses are basically just shirts adapted to female anatomy, so I'm not even sure if we should distinguish them from shirts, and tight-fitting t-shirts (similar to girly-shirts) have found their place in masculine fashion as well.
At this point it probably comes down almost entirely to intent. It would have to be something like a girl adopting a style of dress for the express purpose of passing as male, while still identifying as female. Or being a drag king I guess.
Of course, this is relative to culture. If you're in, say, Saudi Arabia, there's still clothing that is 100% masculine coded.