For most travelers, 2 days is the perfect amount of time to experience the core highlights of Osaka without feeling rushed. A two-day itinerary typically allows you to split the city by its main districts: the northern "Kita" area (Umeda) and the southern "Minami" area (Namba/Dotonbori). On Day 1, you can visit the historic Osaka Castle, explore the high-tech Umeda Sky Building, and enjoy the massive Osaka Aquarium Kaiyukan. Day 2 can be dedicated to the neon-lit food paradise of Dotonbori, the trendy shops of Amerikamura, and the traditional atmosphere of the Shinsekai district. If your goal is specifically to spend a full day at Universal Studios Japan, you may want to add a third day, as the park can easily consume a 10-hour window. However, because Osaka is primarily known for its vibrant street food culture and shopping rather than a vast list of individual landmarks, 48 hours is usually sufficient to capture the city's unique "Kuidaore" (eat until you drop) spirit before moving on to nearby Kyoto or Nara.