I wonder if we can and if we can't what are the cinsequences? They will just cancelled the game or we will need to pay ?
On broad rule: it depends on your local law and how they apply to you within the third party that "feels damaged" by your copy-product.
Generally speaking the US is the most strict; a notorious recent case is Nintendo suing and obtain a piracy settlement with a couple in Arizona ( ref) of about 12$million.
Such laws do mostly "apply" when the copyright holder feel damaged by your work, there are companies who are more strict (like Nintendo, which is basically the wrost not giving a shit even for fan's made free game) and other who are pretty much lasseiz faire ("let people do": less inclined to sue fans) like Valve who are notoriously know for even working with the mod community fan/game to growth in their own product.
It's a complicated alchemy made by local laws, copyright holder, economic situation (starving companies are known to get more aggressive, while companies who shut down are pretty much inactive into protecting their IP)
TL;DR: There are lot of developer/designer/artist: don't feed big and deaf companies: get together with other people and build your own IP/arts/stuff!
I'll add that from Itch.io's point of view, we're not going to check beforehand, unless you're selling your game for money, and then only to make sure the game itself doesn't belong to someone else. We don't normally look at the assets used.
The moment someone complains, however, we're going to look into it. That's mostly because Itch is hosted in the US, and US law holds web services like this responsible if they don't take active measures once they're notified of a problem.
Fortoj is right. Make fan games if you love a franchise that much. You might get lucky, especially if you make no money from it. But it's best to use your own original characters, stories and so on. Buy art and music if you can't make your own, or find some that's under a Creative Commons license. Own your work, it's a lot safer that way, and you can do a lot more.
While the above replies are technically correct, I would advise to be more strict.
What are you asking here is basically: "can I post illegal content here?"
Stop for a minute and think. Like… seriously? Do you realise what this implies? You can be sued, you can go to court, you can have to pay HUGE fines and even go to prison… all this for what? Nothing to gain at all.
There are thousands of free assets out there. If you use free assets you will have a legit project that you can freely upload anywhere, maybe build upon it or whatever… why on Earth would anyone use illegal content instead, dooming the project itself from day 1?
As someone who's created transformative fair use fan works (aka 'rom mods') for older games as well as mods for semi-newer games (FF12), I feel that I have a bit of perspective to offer here.
There are several choices but here are the ones that stick out to me:
-Make a fan game but have it be non-profit; know that it will go poof if the copyright holder gives a damn about it.
-Make an original game and have it be completely ignored in the absolute glut of great games coming out now and in the near-future. Be lost in the crowd and lose all motivation for being 'noticed' by senpai or otherwise.
-Make a non-profit free modification of an existing game that requires that game in order to work; realize your work won't ever be standalone but do it for the love of the game.
I chose the 3rd option but my most notable/useful mods have to be the simplest ones. I created a 'bug fix' patch/mod for Chrono Trigger (SNES) and a 'Cutscenes Unleashed' mod for FF12 that removed some black bars/crap that Squeenix left in during the PC port.
I'd love for more people to make original games. For example there's an absolutely jaw-dropping amazing rom mod called Metroid: Rogue Dawn. Completely original character very loosely based on existing IP; completely original environments, storyline, and all that. Change some names and it would be an amazing indie game. But nope; they not only insisted on making it a rom mod but also on having the actual name just be a subtitle under the Metroid brand. It got some initial buzz but died off shortly thereafter because other games come out all the time. Effectively it was some glorified fanfiction but NONE OF THAT MATTERED because the actual gameplay was just so damn good. You could leave out all the story and none of it would matter!
There were some other games, one of which was the 'Dragoon X Omega' series by 'SliverX' (yeah I know) but outside of the really terrible naming scheme, they never bothered to port the game ideas and story stuff to any other platform. Bit of a shame :(
My honest advice is to just grab a game engine and mess around with it. Try a bit of everything. RPG Maker, GoDoT, Unity, whatever. Make some prototypes and demos of stupid little trash games and bit by bit you can grow it into something amazing and worth releasing. Do all this on the side and then do a crowdfund to turn the prototype into a full game. If funded, proceed to release. If not? Keep it as only a hobby.
The easiest and quickest way to money in the current age is to hire an artist and make a clone of yet another gambling-focused 'gacha' game aimed at the JP/KR/CH markets. Or do even less by buying up some cheap patents and suing people in Texas courts, lol.
That said though, you will have the easiest path in having the ability to do what you want how you want with as little friction as possible. Biggest issue with rom modding is the need for external tools/editors (or coding some yourself) while fan games face the copyright issues. There's a copyright on Pokemon but zero copyright on the idea of capturing wildlife and making them fight each other in battles.