There are bridges, depending on which dApp platform you would use. With Ethereum, if you use the web player for unity, you can use the ExternalCall, to call the web3 js provider and have metamask as a requirement to do calls to smart contracts etc.

Other options would be to use the json-rpc interfaces.

So there are options, without knowing the details of the game, that is briefly described. Different blockchains have different methods. Remeber that doing microtransactions and high speed stuff is not viable on many of the blockchains due to the slow transaction speed and easy to cause congestion as well as tx costs.