So, I have been checking for flights for this summer but they are really expensive compare to out season.
I am planning to go to Osaka and I found it difficult to find a good fare. I found this one and, as you can see, I would have to pay 845 EUR.

However, I was "playing" with ITA Matrix I found out that I can get the same itinerary paying about 300 EUR less. You can check that fare in this PDF file. If that's it's like I think the saving is really impressing.

However, I'm not sure if I buy this ticket the luggage will arrive at my final destination or I will have to pick it up and do the checkin again every time as it is a multidestination flight. So maybe you can help me to understand if I will have to do the checking in every destination or I will only have to wait inside for the next flight. To check that I think the PDF file from ITA should be enough.

Thanks for your help!

I have seen some simple (non-stop each way) round trips where buying two one-way flights was less expensive than buying a round trip of the same flights on the same airline. These were on airlines like UA and AC. Of course, there are change fee implications of two one-ways versus a round trip.

When there are connecting flights, it would be riskier to split the tickets between the connecting flights (as opposed to between the outbound and return), since a misconnect on separate tickets is worse than a misconnect on the same ticket.

So you might try pricing out one-ways of MAD->KIX and KIX->MAD for comparison.

Thanks for your answer. I know it's usually riskier. However when I look at the fare details at ITA Matrix it seems that actually the fare at the end is same as a roundtrip fare (it says "round trip fare"). Maybe someone can check the PDF file and tell me if I'm wrong.

I think you will be fine. This is a round trip fare. You can just check-in your back to Osaka. It just happens that the cheaper fare you found (fare class "V") was not found when you don't specify the stop. You're lucky!

Like they said. The fact that you're seeing the price on ITA as two fares, and that it says "round trip" is the indication that regardless of what you started with this is a round trip fare. I do this all the time to force a specific routing. On ITA "multi-city" doesn't mean anything more than "I want to do something other than A-B-A (round trip) or A-B (one way).

When I recently wanted to fly ORD-IST-SIN and then SIN-anywhere-ORD, the only way I could force the layover in IST was to do a multi-city rather than asking for ORD-SIN, SIN-ORD.

This can happen when the pricing logic does not allow the cheapest fares on each segment to be combined as a single fare. This check does not seem to be made when you price the segments individually even though it is a connection. I don't think that the airlines have thought to forbid this in the T&C.

I've seen this a lot in flying to assorted places on the Continent via London. The London market, both from the U.S. and from many Continental cities, is very competitive. Fares in both directions tend to be low. The market from the U.S. to those Continental cities is usually much less competitive, so fares tend to be higher - often higher than the sum of the other two, even if you book exactly the same flights.