It’s been a while but I used to live in Osaka, about 20-30 minutes from the downtown core! Best sightseeing spots to hit: Osaka Castle, Harukas 300, the Daisenryo Kofun, Osaka Aquarium. Best partying spots imo: GHOST Osaka, Space Station PC & Retro Bar, Bar Moonwalk, and tons of smaller bars/karaoke places/small restaurants to visit in the back streets!