This is totally an appropriate use of the forum! some of this may be obvious to someone who‘s already living in japan but it could be useful for people visiting too, so I’ll say some more generic stuff.
Namba is the extra touristy area with the glico man (who has recently been ruined by becoming a big bunch of LEDs instead of neon), big animatronic crabs on restaurants, etc. It's dumb but worth seeing once and also my dentist is there lol. the majima section of yakuza 0 is based on this area.
Umeda is a much cooler zone, more college town, lots of clothing shops and things to look at. I love the store tentenjou (https://twitter.com/selectshopten2) for bright pink goth stuff and whatever, they often have an artist hanging out there who'll make something for you on the fly.
obviously denden town is where the games be, and game tantei is probably the better shop. shinsekai nearby is where you'll find a bunch of arcades like multiple branches of zarigani, etc. The story I told about detective-style hunting down SNK's Yosaku happened there.
Osaka castle is kind of nice to visit even though it's touristy too? Also my buddy Masaya Matsuura kept telling me to go to Nara because it's not far from Osaka, and he says it's the seat of japanese culture and also he was born there, but I never did it and he was disappointed.
Osaka is pretty small-feeling compared to tokyo but my main advice is just walk around a bunch of places, maybe with a plan in mind like checking out x restaurants or bars, or as I did, trying to hit up every book off or something, and just stopping along the way at whatever's interesting. There's a mall that has a bunch of record shops in it in osaka... somewhere... I've honestly forgotten, dang it. there are several shops in the area because it used to be where all the music industry stuff happened I guess?
have a coooool time out there!
I'm gonna counter @Karasu's assertion that the japanese craft beer scene is more interesting than the north american scene - there are a lot of IPAs out here to be sure, but we also have a HUGE variety of stuff where japan is all "wheat or rice beer with one extra thing you can sort of taste" or "we use X kind of rice instead of Y" and there's almost no flavor difference.
I got extremely disappointed when I found out the goya beer (from okinawa!) isn't even bitter, and maybe it was you who said that, @SU2MM ??