I don't know Osaka well but if it is anything like the rest of Japan street approaches seem like the absolutely least effective way to meet women, especially since you mention that personality is somewhat important to you. Did you say you're a university student? If so, it seems you could just target the different classes/organizations full of girls seeking foreigners (e.g., take a class in a European language, do language exchanges - basically anything obviously "intercultural"). If you're German (?), basically any German themed activities will just be a buffet of girls with a German fetish.
Most Japanese girls are paranoid about men (and Japan does have a fair number of perverts) so if you are limiting yourself to girls willing to go fuck a guy they meet on the street, you are looking at a pretty small market. If you want to approach random girls, at least go to the part of town that caters to foreigners and hang out at a cafe or bar. That way you can have a decent conversation, it doesn't scare her off by making it obvious you are hunting for women, and many of the girls there will be actively looking for men and advertising the fact by studying English in a public place.
Most Japanese girls are paranoid about men (and Japan does have a fair number of perverts) so if you are limiting yourself to girls willing to go fuck a guy they meet on the street, you are looking at a pretty small market. If you want to approach random girls, at least go to the part of town that caters to foreigners and hang out at a cafe or bar. That way you can have a decent conversation, it doesn't scare her off by making it obvious you are hunting for women, and many of the girls there will be actively looking for men and advertising the fact by studying English in a public place.