While playing through Demon's Souls, it's only a matter of time before another player invades. The first time this happens, it can be quite the shocking affair. More likely than not, players aren't ready to jump into PVP, and oftentimes the opposing players is far more prepared and better equipped. This usually results in a swift defeat, and it frequently comes at the worst times possible (ie. on the way back to retrieve souls). Players have argued over whether PVP should be forced in Souls games since they first became popular, and while there's no easy answer to that question, there is an easy solution to invaders in Bluepoint Games' remake.
Naturally, this solution doesn't come without a cost, and a hefty one at that. Players will have to decide if the benefit of never having to deal with an invader is worth what they're giving up, a decision that will surely be different for each player. Demon's Souls is unforgiving in a lot of ways, and unfortunately this is one of them.
When playing Demon's Souls, players can launch the game offline. When playing offline, the player won't be able to see bloodstains of fallen players, signs left behind by other Slayers of Demons, or Blue Soul Signs. This means that co-op is unavailable completely, but it also prevents other players from invading the world as hostile Black Phantoms. This has been the approach for every Souls game since Demon's Souls, with the ability to co-op being considered a fair trade off for being invaded.
Obviously this isn't a solution for those players that want to play through Demon's Souls together with a friend. Unfortunately, there's no legitimate way to avoid invasions outside of playing offline, but there are some things that the player can do to turn the tide during an invasion. For starters, recognize that the Invader doesn't win if they kill a Blue Phantom, and these phantoms can repeatedly be summoned to continue fighting. Unscrupulous players might also opt to simply force quit the game whenever they are invaded, though keep in mind that this is generally frowned upon by the community.
It would be nice if there was a way to opt out of invasions entirely, but that is not a feature that ever has or likely ever will be included in a FromSoftware Souls game. Instead players wanting to co-op will need to learn to adapt to invasions and deal with them somehow, as it is just a part of what makes Demon's Souls what it is.
Demon's Souls is available now on PS5.