(article updated to 2020)
Osaka is the second most important metropolitan city in Japan after Tokyo. Despite this, it is not a city that offers a lot in terms of tourism if not for food: "kuidaore", a local expression, in fact means "eat to burst".
In any case, in my opinion it is absolutely worthwhile to come to Osaka even for half a day if you have time available and if you are already in Kyoto. Its unique architecture, chaos, kaleidoscope of colors and the sunset over the canal will fascinate you, be assured.
Kyoto is also a more dispersed city than many others (Tokyo in the first place), so plan your trips well in advance.
Make sure you buy the pocket wi-fi from Italy and pick it up as soon as you arrive in Japan at the airport (alternatively you can have it delivered to your hotel). This tool is essential because it allows you to always stay connected to the Internet during your trip. On your return, you can send it by post by inserting it in the envelope that will be given to you and leave it at the airport post office. The best and safest place to buy it is this.
Google Maps works perfectly all over Japan, but if you want to use the site that the Japanese themselves use, download the HyperDia app (it's also in English) to find the timetables of public transport.
Japan Rail Pass: considered essential by many, in my opinion it is not always the case. My advice is to make a precise and feasible itinerary before leaving and to calculate with HyperDia how much you will spend with the means of transport. Very often making this purchase is futile. If not, it must be bought from Italy on this site.
Powerbank: always better to buy one so as not to remain with the phone down.
Money: here's what NOT to do before leaving, to exchange money in Italy. Changing is never convenient, so it's best to exchange money as soon as you arrive at the airport. However, bring a certain amount of cash money (needless to say that no one will steal it) because it can happens that the cards give problems, especially to ATMs. I recommend you top up your PostePay (the classic yellow, not the Evolution one) and if you have an ATM or a credit card it is always better to contact your bank to warn it that you will make payments in Japan (if you do not warn, they could block the card); also ask to put the card in "worldwide payments" mode on. Keep in mind that in Japan cards are used much less than in the West, so it is always good to have a certain amount of cash with you. Many restaurants only accept cash.
Health insurance: it is good to be careful and buy a valid insurance that covers as much as possible (you never know what can happen). In Japan health care is both public and private, and being outside the European Union, prices and bureaucracy are different. You can buy it here.
HOW TO GET
From Kyoto: take one of the Limited Express trains. [30 minutes travel, cost 1,560 yen]
From Tokyo: to do it first, it is advisable to take the Shinkansen Nozomi, which is the fastest compared to the others [153 minutes of travel, cost 15,010 yen]
From Kansai International Airport: take the Haruka Express train. [50 minute journey, 1,390 yen]
HOW TO MOVE
In Osaka there is a very efficient and widespread subway, so it is the best way to use to move around the city.
WHAT TO SEE
UNIVERSAL STUDIOS JAPAN This is the first Universal park to open in Asia, perfect for those who love American cinema. Among the worlds that can be visited: Harry Potter, Jurassic Park and The Shark. [times 09:00 - 19:00, website, price 7.400 yen, how to get there: from Osaka central station take the JR Yumesaki Line train to get there in 15 minutes]
OSAKA AQUARIUM It is one of the largest in the world, with 14 pools that recreate the natural environments of 10 areas of the Pacific Ocean. [hours: 10:00 - 20:00, price 2300 yen]
OSAKA CASTLE Commissioned by the warlord Toyotomi Hideyoshi and built in the 16th century, it represents one of the most important monuments in Japan. [timetable: 09:00 - 17:00, closed from 28 December to 1 January inclusive, cost 600 ¥, how to get there: a few steps from the Tanimachi 4-chrome subway stop (Tanimachi and Chuo lines)]
DOTONBORI Large district of Osaka, its main attraction. Characterized by a multitude of colorful and local signs to eat street food, this street, and its parallel that runs alongside the canal, is the heart of nightlife and a symbol of the city itself. Already in 1600 it was considered a fun area par excellence and, despite the bombings of the Second World War destroyed many of the previous buildings, Dotonbori still shines more than ever. Here you can taste all the local specialties: okonomiyaki, takoyaki, yakisoba, gyoza and sushi. In this regard, I point out that in many restaurants in the area you can eat the famous puffer fish (fugu), you will recognize them because they have a puffer fish right at the entrance. Crossing the Dotonbori on foot, you arrive at the Ebisubashi bridge where the famous Glico sign stands with the athlete running. From here you get to NANBA (from the old name of Osaka, Naniwa), another entertainment area where you will find pachinko rooms, discos and restaurants. I would also like to point out the SHINSAIBASHI extended covered shopping area.
Compared to Kyoto, Osaka has the advantage of being much cheaper in terms of hotel costs, as well as offering a much more lively nightlife. In fact, if Kyoto is the perfect city for a romantic holiday, Osaka is the destination for unbridled fun.
If you want to have fun, I recommend you to stay in Nanba. Alternatively, opt for the station area, tidy, safe and quiet, perfect if you need to leave shortly.
WHERE TO EAT
The whole Dotonbori area is a riot of clubs, restaurants and street food shop windows. You will be literally bombarded with bright colors and signs, so get ready! The symbol of the whole area is certainly the large mechanical crab of the Kani Doraku restaurant, built in 1960.
GYOZAOH DOTONBORI Impossible to miss the huge sign in the shape of Japanese ravioli which dominates the facade. Here they serve street food gyoza with different toppings. [opening 5 pm - 1 am, address: 2 Chome-4-14 Dotonbori, Chuo Ward, Osaka, 542-0071]
TAKOYAKI JUHACHIBAN SONS DOHTONBORI One cannot fail to notice even this sign with gigantic takoyaki. Take the ticket with what you want to eat at the automatic payment machine and queue for your favorite octopus balls. [opening 11 am - 9 pm, website, address: 〒542-0071 Osaka, Chuo Ward, Dotonbori, 1 Chome − 7−21 中 座 く い だ お れ ビ ル 1F]
SUSHIZANMAI DOTONBORI Acclaimed by all youtubers, this chain of sushi restaurants has become an institution for tourists. I wanted to try it too but honestly I didn't like it. I also point it out for those wishing to experience. [open 24h, website, address: 〒542-0071 Osaka, Chuo Ward, Dotonbori, 1 Chome − 7−21 中 座 く い だ お れ ビ ル 1F]
ICHIRAN RAMEN DOTONBORI Another Mecca for fans of Youtube and ramen. Very cheap and always so crowded. [open 24h, website, address: 1 Chome-4-16 Dotonbori, Chuo Ward, Osaka, 542-0071]
KUSHIKATSU DARUMA DOTONBORI Probably the most famous place in Osaka where you can taste the famous fried skewers. Open since 1929. [opening 11:30 am - 10:30 pm, website, address: 1 Chome-6-4 Dotonbori, Chuo Ward, Osaka, 542-0071]
RIKURO'S CHEESE CAKE A real world-renowned institution, this is the realm of the noble Japanese cotton cake. Here you can admire the preparation of the famous dessert from the showcase of the open kitchen. The cake is not sold in fact but only in whole shape, but if you are two of you will still be able to finish it (a cake is made up of about eight vanishing slices like a cloud). Buy it on arrival at Osaka station or before leaving, as the shop is right there. [opening: 9:30 am - 9:30 pm, website, address: Unnamed Road3-chōme NanbaChūō-ku 2, Chuo Ward, Osaka, 542-0076]